FORENSICS
Top Shelf Science: Forensics
BACKGROUND
What Is Forensic Science?
"Forensic" is
derived from the
Latin forensis,
meaning a public
forum where, in
Roman times,
senators and
others debated
and held judicial
proceedings.
Forensic science is the study and application of science to
legal matters. "Forensic" is derived from the Latin forensis,
meaning a public forum where, in Roman times, senators
and others debated and held judicial proceedings. Forensic
science and criminalistics can be used interchangeably and
cover a multitude of disciplines. The first seven subjects in
the list below are those most commonly applied in crime
laboratories.
Chemistry
Biology
Firearms
Document examination
Photography
Fingerprints
Computer technology
Toxicology and drug analysis
polygraphy
Anthropology
Psychiatry
Odontology
Enginnering
Geology
Entomology
Physics
Pathology
Environmental science
A forensic scientist primarily studies the different types of evidence recovered from a
crime scene. The forensic scientist must be prepared to testify as an expert witness at a
trial or hearing. As such, he or she presents data, evaluates evidence, and renders an
impartial opinion to the court. A forensic scientist will also perform scientific research and
train others in the area of forensic science.
Evidence
Evidence is defined as “anything which is legally submitted to a competent tribunal as a
means of ascertaining the truth of any alleged matter of fact under investigation before it”.
In other words, anything that is submitted to a court to determine whether an accusation is
true.
In the law, evidence can be divided into two general categories: direct and circumstantial.
Direct evidence is evidence that, if true, prove a fact without any inferences; examples
include eyewitness observations and/or video recordings of a crime taking place. Some
evidence does not prove a fact but may be strong enough to imply a fact or event; this
type of evidence is called circumstantial evidence. The greater volume of circumstantial
evidence there is, the greater weight it carries. Probability and statistics come into play
here.
Evidence can also be classified as testimonial, physical, or negative. Testimonial evidence
is evidence given by an eyewitness, usually under oath. Physical evidence is any object or
material that is relevant in a crime. It can be most any tangible thing, as large as a plane, as
small as a hair, as fleeting as an odor, or as obvious as a demolished federal building.
2
Both physical and testimonial evidence can be either direct or circumstantial. Here are
examples of each:
•
•
•
•
Direct testimonial evidence: under oath, a witness states that she saw the accused
stab the victim.
Circumstantial testimonial evidence: under oath, a witness states she saw the
accused, who holding a knife, enter the victims house. She then heard screams.
Direct physical evidence: A security tape shows the accused stabbing the victim.
Circumstantial physical evidence: the fingerprints of the accused were detected on
the handle of the knife that was used to kill the victim.
Forensic scientists are most concerned with the analysis of physical evidence. Edmond
Locard (1877-1966), a French forensic scientist, espoused that there was always an
exchange or transfer of material when two objects came into contact. The methods of
detection may not be sufficiently sensitive, timely, or technologically advanced to
ascertain its impact; nevertheless, a transfer takes place. This tenet is known as Locard's
principle.
“Every contact leaves a trace.” - Locard's Principle
So, What Good Is Evidence?
Physical evidence can:
•
•
•
•
•
prove that a crime has been committed
corroborate testimony
link a suspect with a victim or with a crime scene
establish the identity of persons associated with a crime
allow reconstruction of events of a crime
The Rules of Evidence define what evidence is acceptable (admissible) and how it can be
used for the jury. Most of all, evidence must be relevant, meaning it must prove something
(probative) and address the issue of the particular crime (material). Evidence is
admissible if it is reliable and the presenter of such evidence is credible and competent.
Generally, hearsay is inadmissible in criminal court because it is not reliable nor was it
taken under oath and therefore does not allow for cross-examination.
The presenter of scientific evidence, the expert witness, must establish
her credibility through credentials, background, and experience. Two
legal decisions have largely governed the admissibility of scientific
evidence: the Frye standard and the Daubert ruling.
According to the Frye standard (Frye v. United States, 1923), the
interpretation of scientific evidence must be given by an expert witness
and have gained" general acceptance" in the particular field of study.
To meet the Frye standard, the court must decide if the questioned
procedure, technique, and principles are generally accepted by a
meaningful segment of the relevant scientific community. This case
does not offer any guidance on reliability.
Two legal
decisions have
largely governed
the admissibility
of scientific
evidence: the
Frye standard
and the Daubert
ruling.
3
The Daubert ruling (Daubert v. Merrell Dow Pharmaceutical, Inc., 1993) stated that the
Frye standard is not an absolute prerequisite for admissibility of scientific evidence. This
rule applied only to federal courts; however, states were expected to use the decision as a
guideline in setting standards. The trial judge must assume responsibility for admissibility
and validity of evidence presented in his court. Guidelines offered for judgment include
the following:
1.
2.
3.
4.
5.
The scientific theory or technique must be testable.
The theory or technique must be subject to peer review and publication.
Rate of error or potential errors must be stated.
The technique must follow standards.
Consideration must be given as to whether the theory or technique has
attracted widespread acceptance within a relevant scientific community.
The Daubert ruling came about in response to a rapidly changing technological society.
For new theories or techniques (such as DNA fingerprinting), unacceptable delays in
admitting reliable evidence led to the decision.
Individual vs. Class Evidence
The best evidence is the type that can be individualized to a
single, specific source, so that there is no doubt as to what the
source of the evidence is. This type of evidence can place a
suspect at a crime scene, associate a suspect with a victim, and
sometimes even prove who committed a crime. Human
characteristics that can be linked to or individualized to a
particular person are fingerprints, DNA, handwriting, and
voiceprints. The forensic scientist is always trying to individualize
evidence so that it will have more value in the case. If this is not
possible, the evidence may be found to be consistent with a
particular source. This is called class evidence. Class evidence
alone may not be very convincing in a crime, but if there are many
different types or pieces of class evidence, the value can be
considerable. Examples of class evidence are hair, fibers, soil, and
glass fragments.
Class evidence is
associated with a
group.
Individual
evidence is linked
to a particular
source.
4
For example, a tuft of fabric is found at a crime scene. It can be identified by chemical
methods as to what type of fabric it is. Suppose it is found to be a polyester. Is this
information helpful? Further examination can classify the fabric as part of a blue polyester
shirt. A particular suspect may own a blue polyester shirt. But how common is this? Now
suppose the fabric were ripped from the suspect's shirt in a large enough piece so that it
can be matched exactly to the hole in the shirt, like a jigsaw puzzle. The piece of fabric is
now uniquely associated (individualized) to the suspect's shirt.
Class evidence is associated with a group or class, like polyester or blue polyester shirts.
Individual evidence can be linked to a particular source with a high degree of probability,
like matching the torn fabric to the shirt. Individualization always involves a comparison.
5
Identification and Individualization
Complete the following in your bound journal.
Characterizing Your Shoes
1. What are some class characteristics of the shoes you are wearing? Note color, size, brand,
length (in cm), and at least one other class characteristic.
2. How can you individualize your shoe using characteristics that will link them to you and to
nobody else -- regardless of whether someone else’s shoes have the same class characteristics?
Use a photo of your shoe to identify at least two such points of individualization.
Individualizing Pieces of Paper
The scraps of paper in the baggies were originally five index cards that were torn in half
and shuffled. Examine the torn edges using a hand lens or a DinoScope.
3. Attempt to match all five pairs of cards; record the identifying letter/number of each
pair.
4. Of the five pairs you identified in step 3, identify the one pair that you are most
confident match. Take a photograph of the torn side of each of the two pieces side-byside. Download the photo to a computer and transfer them onto a document. Then, add
at least three points of identification that lead you to believe the two halves match (see
the example on the following page). Write a short but descriptive summary paragraph
below the photo. Print a copy for each member of your group, and glue it into your
bound journal.
5. Choose two pieces of paper that do not match. Take a photograph of the torn side of
each of the two pieces side-by-side. Download the photo to a computer and transfer
them onto a document. Then, add at least three points of identification that lead you to
believe the two halves do not match (see the example on the following page). Write a
short but descriptive summary paragraph below the photo. Print a copy for each
member of your group, and glue it into your bound journal.
Conclusions
1. Do the tear patterns individualize the pieces of paper? Explain your answer.
2. Would individualization be possible if a piece of paper was torn into three pieces and the
center piece was destroyed? Explain your answer.
3. What would you expect if pieces of paper were cut with scissors rather than torn? Would
individualization be possible? Explain why or why not.
4. Imagine that the evidence you were examining were scraps of fabric that were cut with
scissors. Would it be more or less difficult to individualize the pieces? Explain why.
6
Evidence Comparison Examples
MATCH
The photo above shows paper piece 2A on the left and 2F on the right. These two edges appear to be the boundary between a
single tear because there are several distinctive edges that match up. All four labeled positions (A – D) have a protrusion on
the left piece, and a corresponding indentation on the right side, at the same position form the end, and with same approximate
size. Additionally, the overall width of both sheets of paper were identical (measured as 5.35 cm). This circumstantial
evidence leads me to believe that these two pieces have been individualized to a single sheet of paper.
*****************************************************************************
NO MATCH
The photo above shows paper piece 2A on the left and 2D on the right. The overall width of both sheets of paper were identical
(measured as 5.35 cm). However, these two edges appear to be distinctly different from each other. For instance, Positions E
and G each show a indentation, but the other piece of paper has no corresponding protrusion at that position. Position F shows
a notch with no corresponding protrusion.
7
Probability and Statistics
"The probability of showers Tuesday is 80%."
"The odds of the Detroit Tigers winning two consecutive baseball games is 20 to 1”.
“The likelihood of winning the lottery is 1 in 250,000."
"The frequency of death in an auto accident is 0.000176."
We deal with probability most every day in one form or another. The law does as well:
"probable cause," "probative," "probability of an accidental match," "weight of evidence,"
and "beyond a reasonable doubt" are all probability terms used in our legal system.
Can evidence be quantified?
Can evidence be valued numerically, like odds at a horse race? Probability (P) is the
likelihood that a certain event will occur. If P = 0, the event will not occur; that is, it will
occur 0% of the time. If P = 1, the event will definitely occur; that is, it will occur 100% of
the time. Probability is calculated as a ratio of the number of actual occurrences to the total
of observations. So, for example, assume your class has 24 students. The probability of
someone wearing something red in your class may be 6 out of 24, or 1 out of 4. So,
Probabilities are often reported in decimal form by multiplying by 100. So, the probability
of someone in your class wearing red is (.25)(100) = 25%.
If there are 850 students in your school, how many of those students should be wearing
something red? Statistically one of every 4 should be wearing something red, so:
(Probability in decimal form) x (Population) = (Number of Occurrences)
.25
x
850 = 213
So, statistically, there should be 213 students in the school
wearing something red.
Let’s try another problem: A different class in your school has
19 students (your school still has 850 students). Only two
students in that class are wearing something yellow. Calculate
the probability of a student in that class wearing yellow, and
determine the number of students in your school wearing
something yellow.*
Wearing something red or wearing something yellow are
examples of independent events, which are events that are
independent of other events.
Probability
is the
likelihood
that a
certain
event will
occur.
8
Now, let’s assume both red and yellow fabric were found near some graffiti in the school
bathroom, and you are asked to determine the number of students in your school wearing both
red and yellow. To do this, multiply the probabilities of each independent event:
(P of wearing red) x (P of wearing yellow) = (P of wearing red AND yellow)
Dividing 2 by 76 gives the probability of finding a student in your class wearing red and
yellow as P = .026, or 2.6%. Please note, this method works ONLY if the events are
independent! If, for instance, people who wear red are likely to also wear yellow because
the two colors are complimentary, then you would need to introduce more complex
statistical procedures. In this course, though, we will deal only with independent events.
Practice: How many students in your school (850 students) would be wearing BOTH red
and yellow?**
These probabilities are gained statistically. You may find that there are more or fewer
students wearing a combination of red and yellow. The Rule of Large Numbers says that
the larger the population, the more likely that the actual numbers will approach those of the
computed probability; that is, the larger the population you are considering the more likely
your calculated number of occurrences will be correct.
Correctly calculating probabilities is critical to making a strong case in court; many cases
have been thrown out of court or lost because the computed probability of a random match
of evidence has been overestimated.
Answers:
* P = 2/19, or .105, or 10.5%; 89 students
** 22 students
9
Probability and Statistics
Complete the following in your bound journal.
1. Usually, evidence is used to link or associate a suspect to a crime. More often
than not, the evidence is class evidence. For example, a blue fiber is found at a
crime scene. Look at your classmates; how many could have transferred a blue
fiber from the clothes they are wearing? How many suspects, then, are in your
class?
2. Suppose the entire student body (650 students) had access to the crime site. How
many suspects would there be based on the statistics from your class? (Clearly
show all relevant calculations!) Is the blue fiber evidence of value? That is, does
it do a good job of reducing the number of suspects down to a small number?
3. Suppose that along with the blue fiber, an orange fiber was also found. Does the
combination of a blue fiber and an orange fiber improve the evidentiary value?
Explain why. (Clearly show all relevant calculations!)
4. Does the number of characteristics of a material and/or the number of different,
relevant objects found at a crime scene improve the probability of matching the
evidence to a single suspect? Why or why not?
5. Camden has the following demographics:
•
•
•
•
•
•
Female residents
Male residents
Unmarried residents
Asian residents
American Indian residents
Caucasian residents
2206
1787
1712
20
2
3937
a) A suspect is described as a male, Asian resident of Camden. How many people
fit that profile? Would that characterization be of value?
b) A suspect is described as a female, married, and Caucasian. How many people
fit that profile? Would that characterization be of value?
10
Hair as Forensic Evidence
What Is Hair?
Hair is a filament composed mostly of keratin,
a tough protein polymer of amino acids that
makes the hair strong and flexible. Hair is
produced in a bulb-shaped pocket in the skin,
called a hair follicle. At the end of the follicle
is a network of blood vessels called the papilla
that supply nutrients to the hair and help it
grow. The sebaceous gland secretes oils to the
hair to keep it conditioned. Above the follicle is
the hair shaft, which is made of dead cells.
Why DO We Have Hair?
Hair provided our ancient ancestors with insulation to protect them from extreme
temperatures as well as from harmful sun rays. It may have even served as camouflage,
as it does in many animals. These days, we have clothes and sunscreens; however, 80%
of lost body heat is through the head, so a good crop of hair can act as an insulator.
Hair at specific places on the body has a specialized purpose; for example, hair in our
nose and ears acts as a dust filter; eyebrows were meant to shield our eyes from
excessive sunlight and block sweat from our forehead.
What Attributes of Hair Make It Useful in Forensic Science?
There are about 100,000 scalp hairs on the average person. At any one time, 80--90% are
growing; the remaining are in the process of separating from the hair follicle and
eventually falling out-at a rate of about 100 a day. Not only is hair common, but it is
quite durable and is resistant to physical and chemical degradation. It is also persistent in
that it tends to cling to things, such as fabrics. Examination of hair cannot determine sex
or age. However, new laboratory techniques have enabled DNA extraction from hair
under favorable circumstances. Nuclear DNA can be found in the hair root or adhering
tissue and mitochondrial DNA in the hair shaft.
11
Macroscopic Examination of Hair
Complete the following in your bound journal.
1. You should have brought some of your own hair from a hair brush; if you
haven’t, run your fingers lightly through your hair until a strand is dislodged (do
NOT pull – it needs to fall out ‘naturally’). Tape the hair strand in your notebook
and examine it with a hand lens. Record any characteristics that can be used to
describe your hair.
2. Repeat step 1 on a strand of hair that you forcibly pull out of your scalp.
3. How can the characteristics you listed be used to exclude a person as a suspect in
a crime (be specific!)?
4. What differences do you notice between the two hairs? How could the
differences be useful to a forensic scientist?
12
The Morphology of Human Hair
Structure
A hair shaft is composed of three parts-the cuticle, the cortex, and
the medulla. The cuticle is the clear, outside covering of the hair
shaft. It is made up of tough overlapping scales, such as on a fish or
like shingles on a roof.
The cortex is made up of keratin molecules aligned parallel to the
length of the shaft. Embedded within the cortex are pigment
granules that give hair a lot of its color (black, brown, yellow, or
red). Gray or white hair is the absence of such granules.
The medulla is a row of cells running along the center of the cortex
like a canal. It may appear dark or translucent depending on the
presence of air, liquid, or pigments, and it can be continuous,
interrupted, or fragmented. When the hair shaft is darkly
pigmented throughout the medulla and the cortex, the pattern is said
to be solid. When no medulla is present, the pattern is absent.
Medulla Pattern
Continuous
Interrupted or
Intermittent
Fragmented or
Segmented
Absent
Solid
Description
Picture
One unbroken line of color
Pigmented line broken at regular
intervals
Pigmented line unevenly
segmented
No separate pigmentation in the
medulla
Pigment is so dark that you cannot
see the medula
Forensic scientists characterize hair by measuring it medullary index (MI). The medullary
index is the diameter of the medulla divided by the diameter of the hair:
MI = diameter of the medulla
diameter of the hair
When the medulla pattern is solid, no comment can be made about MI. When the medulla is absent, an MI
can still be calculated (because you will be able to see the boundaries of the empty channel).
13
Diameter
The diameter of human hair ranges from 25 to 125 micrometers (µm). Generally, individuals
have small variation within the type of hair (i.e., scalp, beard, chest, pubic, etc.).
Because the diameter of a hair shaft is so small, you will need to utilize a micrometer to measure
it. To do so, place the hair on the micrometer and take a photograph of it at high magnification.
The width of the lines on the micrometer are .2 mm (200 µm). You will compare the width of
your hair to the width of the line, creating a ratio equation to calculate the actual width of your
hair:
Actual width of your hair
Actual width of the micrometer line
=
width of your hair in the picture
width of micrometer line in the picture
In this equation, you will measure both of the values on the right side of the equal side with a ruler. The
actual width of the micrometer line is a known value – 200 µm. You will solve for the value in the
numerator of the left side of the equation.
Tip
The tip of the hair shaft will taper to a point if it has not been cut or abused for a while. Hair that
has been recently cut is squared off at the tip, but within two to three weeks it becomes rounded.
Frayed hair or split ends result from dryness and lack of care (no conditioners), harsh chemicals
(bleaches), or overuse of a blow dryer (too much heat).
Fluorescence
Some hair that has been chemically treated will fluoresce when exposed to ultraviolet radiation.
Fluorescence can be diminished by washing and by wear. Nevertheless, fluorescent properties are
useful for comparing hairs of a common origin as well as spotting hairs for collection.
Root
Head hair grows at a rate of about 1 cm per month and is
replaced about every 3 to 5 years with new hair. There are
three stages of growth: the anagen phase (80-90% of hair
follicles at anyone time); the catagen phase, which is an
intermediate stage; and the telogen phase (18-10%), in
which the follicle is ready to push out the mature hair. The
hairs on your brush, comb, or shoulder are telogen hairs and
should reflect that in the bulbous appearance of the root with
little if any follicular tissue around it. Anagen hairs that have
been forcibly removed from the scalp may still have
follicular tissue attached and may have pigment granules
evident since the hair was still growing.
The hair's root is embedded in the follicle, which is in equilibrium with the body's blood supply.
Whatever is taken into the body is distributed into the growing hair. This is important in analyzing
hair for drugs and poisons. Since hair grows at a fixed rate, a time frame of the introduction of a
foreign substance can sometimes be established.
14
Microscopic Examination of Hair
Complete the following in your bound journal.
You will examine the hair samples of all members of your group with a DinoScope. In your
journal, create a table similar to the one shown below, only make yours larger, so you have
room to describe your observations. Add a column for every hair sample you observe.
Characteristic
Length (cm)
Color
Appearance (straight, curly, kinky)
Diameter
Medulla Type
Calculated MI
Tip
Appearance under fluorescent light
Cosmetic treatment (yes or no)
Your name
Partner’s name
Procedure
1. Measure and record the length of your hair sample.
2. Record the color and appearance of your hair sample.
3. Place the hair sample on a microscope slide with a micrometer and add a drop of mineral oil or
glycerin. Anchor it with a cover glass.
4. Start with the lowest magnification of the microscope. Take picture of your hair, being sure to
include both a micrometer line and the hair in the picture’s frame.
5. Calculate and record the diameter of your hair. Clearly show your calculations.
6. Go to high magnification and focus. You need a to be viewing a length of the hair that clearly shows
its characteristics; find one by pulling the hair strand through the liquid under the cover glass.
Change the light to be sure you are seeing the medulla, if there is one.
7. Photograph the hair under high magnification (so that you will be able to measure what is necessary
to calculate MI).
8. Identify the type of medulla.
9. Calculate the medullary index (MI). Clearly show your calculations.
10. Examine and identify the appearance of the tip of your hair sample.
11. Examine the hair under fluorescent light. Record whether or not it glows.
Add to the photos you’ve taken so far so that you have – in your journal - pictures of at least 3
medulla types, at least 3 hair colors, and at least 3 types of tips. Label each of these!
(Proceed to the next page!!!)
15
Other Observations
12. If neither you nor any of your partners have dyed hair, complete steps 3, 4 and 11 on a hair strand
that has been dyed. Repeat with a sample of bleached hair.
13. Pluck a hair from your eyebrow, eyelash, arm, or other part of your body. Complete steps 3, 4, 7, 8,
and 9 on this hair.
14. Examine the root end of your hair samples under magnification. You should look at an anagenic
root that was forcibly removed and a telogenic, mature hair root that you obtained by combing or
brushing. Take a picture of each.
The Cuticle
The cuticle of human hair is difficult to observe under a microscope because it is close-packed,
transparent, and fine. Its structure can be delineated, however, by making a cast of hair.
15. Clean a strand of your hair by pulling it through a folded tissue moistened with alcohol to remove
grease and oil.
16. Place a thin coat of clear fingernail polish on a microscope slide and press your hair into it.
17. After the polish becomes sticky but not dry, remove the hair and examine the cuticle impression at
high magnification. Take a picture of what you observe.
** Note: Casting hair is somewhat difficult; if you make a very good cast, please label the
slide with the identity of the animal and SAVE it for others to observe, should they NOT be
able to properly cast their samples.
Conclusions
1. Be sure all required pictures have been cut out and pasted in your journal!
2. Based on your observations, how can you tell that a hair has been dyed? Bleached?
3. Compare the pictures of your hair and one of your partners’ hairs. Identify and write about the
similarities and differences. What significance does this have? Be sure there are pictures of the two
hairs in your journal.
4. Compare the pictures of the hair you observed in step 13 in the Procedure section to your scalp hair.
Identify and write about the similarities and differences. What significance does this have?
5. Describe the differences you observed in pulled hair vs. hair that falls out naturally.
6. What determines whether hair evidence is class evidence or individualized evidence?
16
Animal vs. Human Hair
Complete the following in your bound journal.
The first question asked in studying hair evidence is whether it is human or animal hair. It is estimated
that there are 70,000,000 cats in the United States, 60,000,000 dogs, and millions of other domesticated
animals. The following lab will explore how animal hairs differ from those of humans. Your goal is to
discover differences in characteristics that will allow you quickly and effectively determine whether a
hair is human or animal.
Procedure
1. Complete the observations you made for human hair in “Microscopic Examination of Hair” (Steps 110 on page 16) on samples of hair from two animals (excluding deer hair), being sure to note the
animals involved. Because the animal hairs have been permanently mounted on microscope slides,
you do not have to complete step 3 of the procedure. To photograph the animal hair with a
micrometer, place the animal hair slide on top of the micrometer slide.
2. The sample of deer hair clearly shows two features of hair:
- Observe and describe the color of the hair along the length of its shaft;
- Observe the hair under a Dinoscope; in this case, you will be able to see the cuticle very
clearly. Describe, draw, or photograph the pattern of the cuticle.
Conclusion
1. Be sure all required pictures have been cut out and pasted in your journal!
2. Explain how a forensic scientist can distinguish whether a hair found at a crime scene is human or
animal. Be as specific as possible.
17
Hair Unit Final Conclusions
Hair is considered class evidence in forensic science. Depending on the circumstances, its evidentiary
value or importance is based on statistics. What are the chances that a hair came from a suspect or a
victim? If there are only three possible suspects, a blonde, a brunette, and a redhead, and the
circumstantial evidence consists of a red hair, then there is a 100% probability that the redhead
committed the crime. However, if all three suspects have red hair, then the probability of choosing the
perpetrator is one out of three. Not good enough! In this case, one would hope for more hair
characteristics, or other circumstantial evidence. As you learned earlier, as the number of characteristics
or objects linking a suspect increases, so does the probability of association or involvement.
1. A class has the following makeup:
Hair Color
Girls
Boys
Blonde
6
4
Brown
4
7
Red
0
1
Black
6
2
a. A red hair is found at a crime scene. Calculate the probability of this characteristic in this class.
b. A black hair?
c. If 75% of students in this class have short hair, what is the probability of finding the student who
left a long brown hair?
d. If there are 630 students in the school, statistically how many boys would have black hair?
e. In this class, two blondes have a fragmented medulla and one other blond has hair longer than
50 cm. How many girls in the school would you expect to have blond hair longer than 50 cm
with a fragmented medulla?
2. HINT: READ the introductory section in this workbook!! The body of a woman was found in the
woods. Some hair fibers found on the body were sent to the crime lab for analysis. The ends of the
hair attached to the body were gray, but the tips of the hair show it had been dyed. The distance from
the root of the hair to the beginning of the dyed area measured 8 mm (.8 cm). Investigators
determined that the victim’s hair had last been dyed on August 1, 2004. On approximately what day
did the woman die? Explain, showing your calculations.
(continued on the next page)
18
3. A woman with long hair is a suspect in a burglary case. At the crime scene, several long hairs were found
attached to a broken lock of the safe. The police obtain a warrant and request a sample of 25 to 50 hairs
from this woman. They tell the woman it is important that they pull the hairs from her head rather than to
merely cut the hairs. The police suspect that the woman was stealing to help support a drug habit.
a. Why is it important that the police pull the hairs from her head rather than cut them?
b. Why is it necessary to obtain 25 to 50 hairs from this woman?
c. The woman denies that she is currently taking illegal drugs and states that she stopped using drugs
about a year ago. Explain how police can determine if the woman has been off drugs for a year.
d. Is the hair found at the crime circumstantial or direct evidence? Explain why.
f. Is the hair found at the crime scene class or individual evidence? Explain why.
4. Someone in your class has stuck a wad of bubble gum on the teacher's desk. Embedded in the top of it is a
hair. Examination finds that it is brown, 5 cm long from bulb to tip, the medulla is fragmented the shaft is
85 µm in diameter, the tip is cut, and there is no evidence of any treatment. Data was collected and
analyzed from a single classroom of 23 students, as shown in the table below. Use the data from table to
calculate the number of suspects in the school of 630 students. Show your work!
Characteristic
Number of students
in the class having
that characteristic
Color
Characteristic
Number of students
in the class having
that characteristic
Medulla
Brown
13
Absent
1
Black
4
Fragmented
14
Red
1
Interrupted
6
Blonde
5
Continuous
2
Length
Diameter
Under 3 cm
3
under 40 µm
8
3-8 cm
8
40 – 60 µm
7
8-15 cm
5
60 – 80 µm
5
15-30 cm
7
Over 80 µm
3
Over 30 cm
Tip
Cosmetic Treatment
Cut
16
Dyed
3
Split
6
Bleached
1
Frayed
1
19
Hair Resources
Comparison of Hair Characteristics by Race
Race
Appearance
European
Generally straight or
wavy
Pigment
Granules
Small and evenly
distributed
African
Other
Color may be
blonde, black,
red, or brown
Kinky, curly, or coiled
Densely
distributed,
clumped, may
differ in size and
shape
Asian
Straight
Densely
distributed
Shaft tends to be
coarse and
straight
Thick cuticle
Continuous
medulla
Cuticle Shapes
coro
nal
(cro
20
Fiber Evidence
Filaments
What Is a Fiber?
A filament is a single strand of material of indefinite length. A fiber is composed of
many filaments twisted or bonded together to form a thread or yarn. For forensic
purposes, fibers are classified as either natural (animal, vegetable, or inorganic) or
artificial (synthetic). Fibers are twisted or weaved together to manufacture fabric,
carpet, paper, rope, and batting.
Fibers
Fabrics
Types of Fibers
Fibers, like hair, are considered class evidence. They lack individuality because they are mass-produced
in such large quantities. For example, in 2001 over 3.5 billion pounds of cotton yarn was produced in the
United States! Some of this cotton was used to make 625 million T-shirts and tank tops, and 184 million
jeans. The probability of finding a match of cotton fibers from a suspect's T-shirt and a victim seem
horrendous. Any characteristics that aids in narrowing the origin of the fiber to a limited number
of sources greatly improve the value of the evidence.
Tables 1 and 2 below lists common natural and synthetic fibers that are currently in use:
Fiber
Hair
Silk
Cotton
Linen
Rayon
Acetate
Fiberglass
Table 1: Common Natural Fibers
Chemical
Source
Description
mammals
insects
plant
plant
plant
plant
sand
protein
protein
cellulose
cellulose
regenerated cellulose
altered cellulose
silica
Common Uses
apparel, blankets
Apparel
apparel, textiles
tablecloths, napkins
apparel, upholstery, curtains
apparel, curtains
insulation
Fiber
Table 2: Common Synthetic Fibers
Trade Name
Common Uses
Acrylic
Aramid
Nylon
Creslan, Acrilan, Orlon
Kevlar
Antron, Meryl
Olefin
Polyester
Innova, Spectra
Dacron, Kodel, Fortrel
Spandex
Lycra, Clearspan
home furnishings, cigarette filters
protective vests, rope, sails, sporting goods
apparel, household furnishings, rope, seat
belts, tents
sportswear, household furnishings, rope, bags
apparel, household furnishings, fiberfill, auto
upholstery, rope
stretchable apparel
21
Types of Fibers
Why Are Fibers Important as Forensic Evidence?
Clothing is made of fibers. Look around you - there are many types of fabric, many colors, many uses.
Fibers, like hair, are easily exchanged so they can provide evidence of personal contact, and possible
association between victim and suspect or object. For example, read an actual case as summarized below:
Five-year-old Melissa Brannen disappeared from a Christmas party the evening of
December 3,1989. The suspect, Cal Hughes, left about the same time but denied having
any contact with her. A search of his car found many fibers and hairs. A few black rabbit
hairs found in the car could have come from Melissa's mother's dyed rabbit coat, which
Melissa was fond of playing with. When she disappeared, Melissa was wearing a Sesame
Street outfit of red tights, red plaid shirt, and a blue acrylic sweater, available, in limited
quantities as it turned out, only from JC Penney.
Blue fibers from the suspect's car matched the only blue acrylic fiber that could be found
in Melissa's room. This provided an additional association between the victim and the
suspect's car. Red cotton fibers from the car matched those from a similar Sesame Street
outfit. The single blue fiber from Melissa's bedroom was found to be identical to those
from a JC Penney, Sesame Street blue sweater obtained elsewhere. An experiment
showed that the probability of a coincidental match of the blue fibers from the car and
those from the Sesame Street outfit was extremely remote. Thus, the association of fibers
linked to Melissa with those found in Cal Hughes's car allowed successful prosecution of
the case. Melissa Brannen's body, however, was never found. (Summarized from Fisher
pp. 115-120.)
22
Chemical Properties of Fibers
Complete the following in your bound journal.
Fabrics have chemical properties, determined by their chemical composition, that describe how they
react when they are exposed to agents that might change their chemical composition. Such agents
include acids and bases, fire, and gentle heat. Specific fibers react in characteristic ways, allowing for
class identification. For example:
• Strong acids may cause some synthetic fibers to shrivel up;
• When fibers are gently heated, they often decompose to smaller molecules. For example, acetate
fibers decompose to form acetic acid that turns blue litmus paper red.
• How a fiber burns, its odor, and the nature of its ash are specific to the types of fabric;
Your goal is to devise a method of using the chemical properties of the reference fabrics to identify as
closely as possible the unknown fabrics that will be provided to your group.
Special Safety Considerations
The chemicals you will be using in this activity involve strong acids, bases, and solvents, all of
which can irritate the skin, cause irreparable damage to your eyes if not immediately washed, and
may dissolve your clothing, as you will see. Wear safety glasses, gloves, and an apron. Clean up
spills, even a drop, at once. Report any accidents to your teacher. Wash your hands after the lab.
PRELAB - Do this at home, to save time!!
You will be conducting three series of tests to distinguish the chemical properties of fibers – chemical
tests, a thermal decomposition test, and a burn test. For each of these, you will do a trial for each known
fiber. All observations need to be recorded in your journal, in neat, well organized tables. Please
construct these tables outside of class time.
1. Chemical Tests Table: you will be observing the reaction of each fiber with Acetone, 6M NaOH,
and 6M HCl. So – in your journal, create a data table that looks like this (only larger, so your
observations can neatly be written in the cells!)
Fiber
Chemical Test Results
6M HCl
6M NaOH
Acetone
Cotton
Silk
Wool
Acetate
Acrylic
Nylon
Polyester
Rayon
Olefin
2. Thermal Decomposition Test: prepare a similar table with the following headings:
Fiber
Appearance of
Smoke
Thermal Decomposition Test
Change in Lead
Change in Red
Acetate Paper
Litmus
Change in Blue
Litmus
Appearance of
Residue
23
3. Burn Test:
Fiber
Behavior as it
approaches
flame
Burn Test
Behavior in the
Behavior as it
flame
leaves the
flame
Odor
Appearance of
residue
Chemical Tests
1. For each test, use only a few short fibers.
2. You will test the HCl and NaOH in the plastic well plates. However the acetone test must be
performed in the porcelain well plates. Because acetone is very flammable, you need to perform
this test far away from any open flame!
3. Arrange your samples in the well plates so that you can test each sample in each of the three
reagents: acetone, 6M sodium hydroxide (NaOH), and 6M hydrochloric acid (HCl).
4. Add enough reagent to cover each sample. Use a toothpick to mush the fabric into the liquid, but be
sure not to use the same toothpick in multiple reagents (that is, each toothpick should touch ONLY
the HCl OR the NAOH OR the acetone). You will need to wait at least 15 minutes before you make
observations; move on to another test while you wait.
5. After 15 minutes, record your observations in your table. It may be helpful to view results with a
hand lens.
Thermal Decomposition Test
6. Place two or three fibers in the bottom of a glass test tube.
7. Place a piece each of red litmus paper and blue litmus paper into the inside of the
neck of the tube (make sure they are not on top of each other).
8. Wet a piece of lead acetate paper. Place the wet lead acetate paper over the top of
the test tube, then cover it with a small round of filter paper. Gently push the filter
paper down to secure it (and the lead acetate paper) in place. You can also use the
test tube clamp to hold the filter paper in place.
9. Holding the test tube with a test tube clamp, gently heat the base of the test tube
over an alcohol burner. Observe what happens to the lead acetate paper, the red
litmus paper, and the blue litmus paper. Observe any residue and the appearance
of any smoke that is emitted. Record all your observations the table.
10. Repeat the procedure for all fabric samples.
Burn Test
11. Use two or three fibers that are about 3 cm long. Hold the sample at one end with tweezers and
bring it slowly into the open flame of an alcohol lamp. Once it catches fire, pull it away from the
flame and place it onto the glass plate. Note all of the observations you wrote in your data table.
12. Fill in your table using words such as scorches, smolders, fuses, melts, glows, shrinks, sizzles,
flickers, flares, sputters, burns fast, burns slow, smoky, sooty, and so on. The ash or residue can be
light gray, black, dark gray, shiny, clumpy, beady, sticky, feathery, and so on.
24
Conclusions
1. Explain why multiple tests of a fabric’s chemical and physical properties are needed to provide class
evidence that has the greatest value.
2. (Warning: this is a challenging question with more than one correct response!) Use the results of all of
the chemical property tests you conducted to create a dichotomus key that can be used to identify an
unknown fiber. Note: you will use the chemical properties ONLY because any single type of fiber
will ALWAYS display the same chemical properties; for example, all cotton will burn in the same
way. However, the physical properties of cotton can differ among fabric; for example, cotton can be
woven in any of the three patterns.
What the heck is a dichotomous key??
A dichotomous key is a tool that allows the user to determine the identity of items in the
natural world. Keys consist of a series of choices that lead the user to the correct name of
a given item. “Dichotomous” means “divided in two parts”, which is why a dichotomous
key gives two choices in each part. In each step, the user of the key is presented with a
statement based on the characteristics of the item; if the item’s characteristics match the
statement, the user is directed to one part of the flowchart; if not, the user is directed to
another part of the flowchart. Ideally, the dichotomous key uniquely identifies each
possible item. For example:
25
Physical Properties Part I: Fibers
Complete the following in your bound journal.
In the last activity, you used the chemical properties of fabric to help identify the type of fabric.
When trace evidence is found at a crime scene, determining the type of fiber is the first step. Once
forensic scientists have determined the type of fiber used in a fabric, they turn to the physical
properties of the fiber and fabric in an attempt to match evidence with reference samples from
suspects. A physical property is any characteristic of a substance that can be measured or
perceived without changing its identity.
Procedure
1. List as many physical characteristics as you can think of that could be used to distinguish a
particular fiber. Then, create a data table in your journal similar to the one below (only larger!) to
record the properties that have evidentiary value for each of the fibers. For instance, “Property 1”
might be “Color”; in the case of the fabric samples provided in this lab, that would not be a
physical property of value because all of the samples are the same color. Each group HAS to
calculate the fibers’ diameters and their appearance under fluorescent light, as well as two other
physical properties (that you define) which help distinguish the fibers from one another.
2. To help you collect the necessary data, observe each fiber with a low-powered Dinoscope. Place
each fiber on a micrometer and take a photograph. You can then use the photos to identify all of the
fibers’ physical properties.
Fiber
Physical Properties of Fibers Results
(Property 1)
(Property 2)
Diameter
Fluorescence
Cotton
Silk
Wool
Acetate
Acrylic
Nylon
Polyester
Rayon
Olefin
26
Physical Properties Part II: Fabrics
Complete the following in your bound journal.
Occasionally, forensic scientists get really lucky and find an in-tact piece of fabric at a crime scene (as
opposed to single fibers). As you learned in the first unit of this course, fabric can be used as individual
evidence if a swatch exactly matches the parent cloth and if a torn edge fits, like a puzzle piece, exactly
to the spot from which it originated. This doesn't happen very often; yet, if more than a fiber exists, the
fabric itself can add to the characteristics of the evidence.
Fabric is classified by its type of weave. In a weave, the lengthwise yarn is called the warp. It is usually
stronger, smoother, and more even, with a tighter twist to it than the weft (the crosswise yarn). The warp
need not be the same material as the weft (this would be called a blend), nor the same color. Sometimes,
the warp and the weft have different diameters in order to produce special effects, such as ribbing.
The three basic patterns are shown below:
Plain
Satin
Twill
The Three Basic Weave Patterns
In plain weave, the warp and weft are aligned so they form a simple criss-cross pattern. Each weft fiber
crosses the warp fibers by going over one, then under the next, and so on. Variations of the plain weave
include bundling fibers so that two twisted weft fibers go over and under two twisted warp fibers, etc.
In a satin weave, the weft fibers float over four or more warp fibers before going under one fiber and
back up. The satin yarns create a more lustrous appearance and the fabric drapes better than plain
weaves, but they are not durable.
Twill is a type of fabric woven with a pattern of diagonal parallel ribs. It is made by passing the weft
thread over one or more warp threads and then under two or more warp threads and so on, with a "step"
or offset between rows to create the characteristic diagonal pattern.
27
Physical Properties Part II: Fabrics
Complete the following in your bound journal.
Procedure
1. In your journal, create a table to record the properties of each of the fabric samples you
have been using in this unit.
Fabric
Physical Properties of Fabrics Results
Weave
Warp Thread/mm
Weft Thread/mm
Cotton
Silk
Wool
Acetate
Acrylic
Nylon
Polyester
Rayon
Olefin
2. Examine each fabric sample at a magnification that allows you to classify the weave. Be
sure to check BOTH sides of the fabric – sometimes the weave is easier to distinguish on
one of the sides! Classify each according to the weave.
3. Measure and record the number of threads per mm in the warp and weft direction of each of
your fabric samples. To do this, view the fabric with the micrometer on top of the fabric.
Count the number of warp and weft fibers that fit inside one of the micrometer squares.
Use the fact that each micrometer square is 2mm x 2mm to calculate the number of fibers
per 1mm.
Conclusions
1. Explain how physical properties of both fibers and fabrics can aid a forensic scientist in matching
evidence to a suspect.
2. A single fiber is found at a crime scene and found to match the physical and chemical properties of
the shirt that a suspect was wearing at the time of the crime.
a. Is the fiber evidence circumstantial or direct evidence? Explain your answer.
b. Is the fiber evidence class or individualized evidence? Explain your answer.
28
Putting it all Together: Identifying an Unknown
Complete the following in your bound journal.
Your goal is to use the chemical and physical properties you made of the reference samples to identify
two unknown samples provided to you (one will be a fabric, while the other will be a fiber sample). Be
sure to record what you are doing, the order you are doing it, and the results in your journal.
•
Record the sample numbers you receive in your journal.
•
Begin by examining the physical properties of each unknown, including photographing the
sample on a micrometer. ( It is important to do this first because the chemical properties
destroy the sample – you don’t want to find out after doing the chemical tests that you don’t
have enough of the sample left to do a proper observation of physical properties. )
•
•
Use the dichotomous key you created of chemical properties to identify each unknown sample.
Once you feel like you have identified your samples, compare the physical properties of each
unknown to a reference sample. Ask Mrs. Damian for a reference sample of the type of fabric
you believe your sample matches. Then, prepare a photo comparison (your sample compared to
the reference sample you believe matches it) of each of your unknowns. Your descriptive
paragraph (below the photo comparison) should clearly indicate the type of fabric and should
describe the chemical and physical properties you are claiming match.
29
Fiber Unit Final Conclusions
A forensic scientist creates the following dichotomous key:
1. An unknown sample is found to have the following results:
Thermal Decomposition
Test
Burn Test
Reaction in HCl
Red litmus paper and lead acetate paper remain unchanged, blue litmus
paper turns red; residue liquefies
Burns quickly when it approaches the flame, remains on fire when removed
from the flame; ash-like residue; smells like burning hair
Does not dissolve – remains unchanged
What is the identity of the unknown?
2. The forensic scientist wants to match the sample to a reference sample that a suspect was
wearing. What else (besides the tests listed above) should the scientist do? Explain why.
30
Chromatography
What is Chromatography?
Chromatography is a process that separates molecules based on differences in their structure. In
general, chromatography involves moving a sample of the molecules you want to separate - the "test
preparation" - over a stationary support. The molecules in the test preparation will have different
interactions with the stationary support leading to separation of similar molecules. Test molecules that
interact strongly with the support will tend to move more slowly through the support than those
molecules with weaker interactions. Additionally, larger molecules tend to move slower than smaller
molecules. In this way, different types of molecules can be separated from each other as they move at
varying rates over the support material.
Chromatographic separations can be carried out using a variety of supports, including volatile gases (gas
chromatography), paper (paper chromatography), liquids (liquid chromatography), and – the support you
will be using - silica plates (thin layer chromatography).
TLC (Thin Layer Chromatography) is a simple, quick, and inexpensive process often used by forensic
scientists to support the identity of a liquid compound in a mixture. For instance, the components of a
dye on a fabric can serve as class evidence to identify the origin of a fiber or scrap of fabric, and these
components can be separated and distinguished through TLC.
How TLC works
A TLC plate is a sheet of glass, metal, or plastic which is coated with a thin layer of silica. A small
amount of the test preparation is placed near the bottom of this plate. The TLC plate is then placed in a
shallow pool of a solvent in a developing chamber so that only the very bottom of the plate is in the
liquid. This liquid is the eluting solution (also referred to as the mobile phase), and it slowly rises up the
TLC plate by capillary action.
As the solvent moves past the spot where the test preparation was applied, each molecule in the test
preparation will be pushed by the molecules in the solvent. At the same time, the molecules in the test
preparation will be attracted to the silica on the plate. As the solvent moves all the way up the plate,
these interactions will cause each type of molecule in the mixture to travel a different distance up the
plate. When the solvent has reached the top of the plate, the plate is removed from the developing
chamber and dried. The dried TLC plate is called a chromatogram.
31
Reading a Chromatogram
A chromatogram is a record of the separated components of a test preparation; often though, the
components cannot be seen by the naked eye and must be treated in order to be visualized. One method
of visualization involves shining UV light on the plates; the plate itself fluoresces everywhere except
where an organic compound is on the plate. Some test preparations may also require visualization by
staining the plates with certain chemicals (iodine is a common choice).
A chromatogram can be quantitatively described by calculating the retention factor (Rf) for each
separated component. Rf is simply the distance from the original spot to the top of the separated
component of the dye divided by the distance from the original spot to the solvent front. For instance, in
the chromatogram below, you would calculate the Rf of the spot visualized from sample one in the
following way:
Rf = distance from the starting point to the top of the spot =
distance from the starting point to the solvent front
1.85 cm
7.15 cm
=
.26
For practice, calculate the Rf values for the the two components of Sample 2*; remember to always show
your wok!
If the color and Rf for a spot from different samples of fabric are similar, there is a good they have the
same origin
* Answers: .52, .85
32
Chromatography
Complete the following in your bound journal.
Dyes used to color fabric may be composed of several constituents. Indeed, there are more than 7,000
different color formulations. Sometimes these can be separated by liquid chromatography.. A
chromatogram of a dye extracted from a colored fabric sample may be compared to others to find a
match. This technique is also used in forensic science to distinguish inks and to analyze for drugs and
poisons.
Special Safety Considerations
Sodium hydroxide solution is corrosive; skin burns are possible so, wash your hands well or wear gloves.
Sodium hydroxide solution is very dangerous to the eyes because it dissolves protein; wear safety
glasses.
Iodine is toxic by ingestion and inhalation. It is corrosive to the eyes and respiratory tract, and is a skin
irritant. Use it in a fume hood only, and do not place your face close to the beaker when you remove the
cover.
Procedure
1. The first step is to extract the dye from the fabric samples. Cut a .5 cm square piece of each colored
fabric sample, or an equivalent wad of thread or yarn, and place in a small test tube.
2. Add 12 drops of O.5M NaOH. Be sure the fabric is immersed. Place in a boiling water bath for 15
minutes. Record the color of the fabric and the color of the extraction solution.
3. While you are waiting for the dye to extract, set up the chromatographic
developing chamber - a wide-mouthed jar lined with filter paper. Add eluting
solution to a height of about .5 cm.
4. Screw the lid on the jar and let it equilibrate for at least 15 minutes.
5. On a precut TLC strip, draw a light pencil line across the strip 1 cm above the
bottom (do NOT “dig into” the silica coating!). Label the bottom with sample
descriptions, spaced evenly across the TLC plate.
6. Once the dye extraction has been in the hot water bath for at least 15 minutes,
remove the test tube and allow it to cool briefly.
7. Transfer each extraction to a well plate so that the capillary tubes can be easily
used. Be sure to keep careful record of which extraction corresponds to which fabric.
8. Using an open-ended, pulled capillary tube, spot one drop of the extracted dye solution on the line,
above its corresponding description. Be gentle so as not to dislodge
the silica gel. Keep the spot small. Repeat 10 times, allowing the
drop to dry before each application. The idea is to get as concentrated
a spot as possible. Discard the used capillaries in the broken
glassware box.P
9. Repeat step 8 for each of the extractions, using a separate capillary
tube for each solution.
10. Lean the TLC plate against the filter paper in the developing
chamber, spot side down. The solvent level should be well below the
dye spot. Replace the cover.
11. When the solvent front is within 1 or 2 cm of the top, remove the
chromatogram and make a mark at the solvent front before it
evaporates. Lay the strip out on a paper towel to dry.
12. Carefully trace any spots that are visible on the TLC with a pencil.
33
13. Observe the TLC under short-wave and long-wave ultraviolet radiation; trace any additional spots
that appear under the UV light with a pencil
14. Invisible spots can sometimes be visualized by immersing the chromatogram in iodine vapor. Prop
your TLC against the walls of an iodine chamber (in the fume hood!), cover it, and gently shake it.
It won't take long, but the developed spots won't last long, as the iodine readily sublimes. Working
in the fume hood and wearing gloves, remove the plate from the iodine chamber; quickly trace any
new spots before the iodine stain fades..
15. Draw or take a photograph of your TLC. Include it in your journal.
16. Calculate the Rf of each spot (show your work!). Compare the Rf values of the spots produced by
the different samples. Even no results (i.e., no extraction of the dye) is an important characteristic
of a sample.
Conclusions
1. When you compared the chromatograms of the different samples, what did you observe? What
conclusions can be drawn from your results?
2. What is the value in calculating an Rf value? Why not just look at the TLC sheet and look for spots
that are in the same horizontal position? (Hint: Think about a real forensics lab…)
3. Identify the source of the unknown sample, and support your identity with a written explanation.
4. Return to the case summary on page 22. Describe what specific tests could be done to make the
most solid link between the evidence and the suspect.
4. Is fiber evidence class or individual evidence? Explain why.
34
Crime Scene Investigation
When a crime scene is discovered, police must take careful yet quick action to collect and document all
evidence found at the scene. To best coordinate that effort, members of Crime Scene Teams generally
have very specific roles and responsibilities. In this course, those roles will include First Responder/Note
Taker, Photographer, Sketch Artist, and Evidence Collector. As you practice these roles over the rest of
the year, your team needs to decide who will take on which role in each of the remaining TWO crime
scene simulations. Choose carefully, based on the skills of the people in your group. Ultimately, your
success, as with real-life Crime Scene Teams, will lie in your ability to work effectively as a team.
Your Crime Scene Team will consist of 4 roles; once the evidence is logged and collected, you will work
together as a team to analyze the evidence found and draw the appropriate conclusions.
FIRST RESPONDER/NOTE TAKER
The first responder is defined as the first officer that arrives at any crime scene. Once the officer
determines that a crime has been committed, he/she has several very specific responsibilities related to
the crime scene. These responsibilities can be summarized with the acronym ADAPT:
o
o
o
o
o
Assess the crime scene – search for potentially injured victims, determine the boundaries of the
primary crime scene, scan the scene for any hazards that may still exist;
Detain the witness(es) – if any witness is present, prevent him/her from leaving; if more than
one witness is present, separate the witnesses from each other to prevent them from comparing
their versions of what happened. A preliminary interview of each witness should include asking
- When did the crime occur?
- Who is the victim?
- Can the perpetrator be identified?
- What did you see happen?
- Where were you when you observed the crime scene?
Arrest the perpetrator – if sufficient evidence points to their guilt;
Protect the crime scene – the primary crime scene must be cordoned off with crime scene tape
so that no unauthorized persons enter the area and contaminate or destroy potential evidence. In
addition, create and maintain a “trash pile” for items that should not be lying about the crime
scene (used gloves, film canisters, etc.)
Take notes – as soon as possible, describe the crime scene (in writing –being as detailed as
possible!) including location of obvious pieces of evidence and the condition of the crime scene
– especially transient evidence. In addition, detailed notes of what evidence was found, when it
was found, who found it, who photographed it, and who collected it must be maintained.
Once the crime scene has been protected, you should call or go get the rest of the Crime Scene Team.
After the rest of the CST arrives, the First Responder is responsible for maintaining THREE separate
logs:
o An Enter/Exit Log: include Time In, Name of Person, Reason for Entering, and Time Out;
o An Evidence Log: include the time and location of every piece of evidence found, as well as the
name of the person who found the evidence and the evidence number assigned to it.
o A Photo Log: include the photograph number, a description of the object or scene in the
photograph, the location of the object or scene, the time and date the photograph was taken and
any other descriptive details that might be relevant. If the photo shows a piece of evidence,
include the evidence number.
35
PHOTOGRAPHER (Adapted from http://science.howstuffworks.com/csi2.htm)
CSTs take pictures of everything before touching or moving a single piece of evidence. The medical
examiner will not touch the corpse until the CST is done photographing it and the surrounding area.
There are three types of photographs a CST Photographer takes to document the crime scene: overviews,
mid-views, and close-ups.
Overview shots are the widest possible views of the entire scene. If the scene is indoors, this includes:
views of all rooms (not just the room where the crime seems to have occurred), with photos taken
from each corner and, if a boom is present, overhead;
• views of the outside of the building where the crime happened, including photos of all entrances and
exits;
• views of the building showing its relation to surrounding structures
• photos of any spectators at the scene
These last shots might identity a possible witness or even a suspect. Sometimes, criminals do actually
return to the scene of the crime (this is particularly true in arson cases).
•
Mid-range photos come next. These shots show key pieces of evidence
in context, so the photo includes not only the evidence but also its
location in a room and its distance from other pieces of evidence.
Finally, the CSI takes close-ups of individual pieces of evidence, showing
any inventory numbers or other identifying characteristics. For these
pictures, the CST Photographer uses a tripod and professional lighting
techniques to achieve the best possible detail and clarity -- these photos in
particular will provide the forensics lab with views to assist in analyzing
the evidence. The CSI also takes a second set of close-up shots that
includes a ruler for scale.
The photographer must also work closely with the Note Taker to compile an accurate photo log. Without
a good photo log, the pictures of the scene lose a lot of their value. For instance, in the investigation of
John F. Kennedy's assassination, the FBI photographers who attended the autopsy didn't create
descriptions of the pictures they were taking, and investigators were later unable to distinguish between
entrance and exit wounds in the photos.
36
SKETCH ARTIST
In addition to creating a photographic record of the scene, CSTs also create sketches to depict both the
entire scene, which is easier to do in a sketch than in a photograph because a sketch can span several
rooms, and particular aspects of the scene that will benefit from exact measurements. The goal is to show
locations of evidence and how each piece of evidence relates to rest of scene. The sketch artist may
indicate details like the height of a door frame, the exact size of the room, the distance from the window
to the door and the diameter of the hole in the wall above the victim's body. As you are recording
measurements, be sure that each object’s position is measured from an immovable landmark (like a wall).
Because time is limited at a crime scene, the CST Sketch Artist usually completes only a rough sketch at
the crime scene, which contains all of the necessary information and measurements at a crime scene.
During the processing of the evidence, the Sketch Artist complete a finished sketch, which depicts
precise measurements of the crime scene and the location of all evidence collected.
Example of a rough sketch
Same scene: finished sketch
37
EVIDENCE COLLECTOR (Adapted from http://science.howstuffworks.com/csi3.htm)
The goal of the evidence collection stage is to find, collect and preserve all physical evidence that might
serve to recreate the crime and identify the perpetrator in a manner that will stand up in court. Evidence
can come in any form. Some typical kinds of evidence a CST might find at a crime scene include:
•
•
•
•
•
•
Transient evidence (temporary evidence such as odors or temperature)
Biological (blood, semen, saliva, hair, vomit)
Chemical evidence (fibers, glass, minerals, narcotics, ink, paint)
Impressions (fingerprints, footwear, tool marks)
Weapons and firearms evidence (knives, guns, bullet holes, cartridge casings)
Questioned documents (diaries, suicide note, phone books; also includes electronic documents like
answering machines and caller ID units)
With theories of the crime in mind, CSTs begin the systematic search for incriminating evidence:
Examining the scene. There are several search patterns available for a CST to choose from to assure
complete coverage and the most efficient use of resources. These patterns may include:
The inward spiral search: the CST starts at the perimeter of the scene
and works toward the center. Spiral patterns are a good method to use
when there is only one CSI at the scene.
The line or parallel search: one or more members of the CST stand
shoulder to shoulder and walk in a parallel line to opposite side of the
room. They continue moving down the length of the room until the
entire area has been searched.
The grid search: a grid search is simply two parallel searches, offset by
90 degrees, and performed one after the other
The quadrant or zone search: the CSI in charge divides the crime scene
into sectors, and each team member takes one sector. Team members may
then switch sectors and search again to ensure complete coverage.
While searching the scene, a CST Evidence Collector is looking for
details including:
38
•
•
•
•
•
•
•
•
•
Is the room in good order? If not, does it look like there was a struggle or was the victim just messy?
Are there signs of a party, such as empty glasses or bottles or full ashtrays?
If there are full ashtrays, what brands of cigarettes are present? Are there any lipstick or teeth marks on
the butts?
Is there anything that seems out of place? A glass with lipstick marks in a man's apartment, or the toilet
seat up in a woman's apartment? Is there a couch blocking a doorway?
Is there trash in the trash cans? Is there anything out of the ordinary in the trash? Is the trash in the right
chronological order according to dates on mail and other papers? If not, someone might have been
looking for something in the victim's trash.
Do the clocks show the right time?
Are there any shoe prints on tile, wood or linoleum floors or in the area immediately outside the
building?
Are there any tire marks in the driveway or in the area around the building?
Is there any blood splatter on floors, walls or ceilings?
The actual collection of physical evidence is a slow process. Each time the CSI finds an item, he must:
• immediately identify it with a standing evidence number,
• have it photographed in the scene by the CST photographer,
• have the sketch artist measure its location from two stationary points,
• appropriately bag and label it using an Evidence Label, and
• make sure it has been entered into the Evidence Log.
Be especially careful that the evidence numbers shown in the photographs and the sketch match the
numbers you put on the labels!
Different types of evidence may be collected either at the scene or in lab depending on conditions and
resources. For instance, latent fingerprints are routinely bagged and sent to the lab for development in a
controlled environment.
39
First Responder/Note Taker’s Checklist
Place a check mark by each of the following responsibilities as completed:

I marked off the area around the victim and kept all unnecessary spectators out.; I didn’t touch
anything other than an injured person.

I interviewed any witness present.

I wrote a description of the crime scene, including documenting all relevant transient evidence.

I documented the pattern used by the Evidence Collector.

I kept a record of everyone who came in or out of the crime scene (handwritten Entry/Exit Log).

I kept a record of the evidence that is found (handwritten Evidence Log); at the end of the period, I
gave the handwritten evidence log to the Evidence Collector.

I kept a record of the description, location and direction of what was photographed (handwritten
Photo Log); at the end of the period, I gave the handwritten photo log to the Photographer.

I prepared a typed, neatly presented description of the crime scene, witness interview, and
Entry/Exit Log, to be turned in.
Name __________________________________________
Date________________________Signed___________________________________
Photographer’s Checklist
Place a check mark by each of the following responsibilities as completed:
 I took multiple overview shots of the overall crime scene from various angles.
 I took mid range photographs of the crime scene.
 I took close-up photographs of all physical evidence encountered, both with and without a ruler.
 I used good lighting and proper focus in all necessary photographs. When lighting was poor, I took
another well-lit photograph.
 My pictures show no crime scene equipment or personnel.
 I worked with the Note Taker to ensure the accuracy of the photo log.
 I checked the note taker’s photo log for accuracy and prepared a typed, neatly presented copy to be
turned in.
 I resized and organized the photos into a printed document, including numbering the photos in the
same order as is indicated in the photo log. Each page should show eight to ten photos.
Name _______________________________________________
Date________________________Signed___________________________________
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Sketch Artist’s Checklist
Place a check mark by each of the following responsibilities as completed:
 I worked with the Evidence Collector to identify all pieces of evidence within the crime scene
labeled
 I measured the distance of each piece of evidence relative to two immovable objects.
 I prepared a rough sketch at the crime scene that shows each piece of evidence in correct position
and shows all measurements taken.
 I prepared a final sketch, approximately to scale, after leaving the crime scene.
Name _______________________________________________
Date________________________Signed___________________________________
Evidence Collector’s Checklist
Place a check mark by each of the following responsibilities as completed:
 I worked within the crime scene, wearing gloves to collect evidence.
 I dusted and lifted fingerprints on surfaces that are too large to be bagged. I did NOT dust for prints
on evidence small enough to be bagged.
 I properly bundled and packaged all materials considered evidence. To the extent possible, the
evidence was begged in exactly the same condition that it was when it was in the crime scene.
 I completed an Evidence Label for each evidence bag.
 I properly sealed all evidence containers and placed them into one or two larger bags.
 I sealed the larger bag(s) with Evidence Tape, which I signed and dated.
 I checked the note taker’s evidence log for accuracy and prepared a typed, neatly presented copy to
be turned in.
Name _____________________________________________
Date________________________Signed___________________________________
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Fingerprints
from http://science.howstuffworks.com/fingerprinting.htm
History of Fingerprinting
There are records of fingerprints being taken many centuries ago, although they weren't
nearly as sophisticated as they are today. The ancient Babylonians pressed the tips of
their fingertips into clay to record business transactions. The Chinese used ink-on-paper
finger impressions for business and to help identify their children.
However, fingerprints weren't used as a method for identifying criminals until the 19th
century. In 1858, an Englishman named Sir William Herschel was working as the Chief
Magistrate of the Hooghly district in Jungipoor, India. In order to reduce fraud, he had
the residents record their fingerprints when signing business documents.
A few years later, Scottish doctor Henry Faulds was working in Japan when he discovered
fingerprints left by artists on ancient pieces of clay. This finding inspired him to begin
investigating fingerprints. In 1880, Faulds wrote to his cousin, the famed naturalist Charles
Darwin, and asked for help with developing a fingerprint classification system. Darwin
declined, but forwarded the letter to his cousin, Sir Francis Galton.
Galton began collecting fingerprints and eventually gathered some 8,000 different samples to
analyze. In 1892, he published a book called "Fingerprints," in which he outlined a fingerprint
classification system -- the first in existence. The system was based on patterns of arches, loops
and whorls.
Sir Edward Henry, commissioner of the Metropolitan Police of London, soon became
interested in using fingerprints to nab criminals. In 1896, he added to Galton's technique,
creating his own classification system based on the direction, flow, pattern and other
characteristics of the friction ridges in fingerprints. Examiners would turn these characteristics
into equations and classifications that could distinguish one person's print from another's. The
Henry Classification System became the primary method of fingerprint classification
throughout most of the world.
In 1901, Scotland Yard established its first Fingerprint Bureau. The following year, fingerprints
were presented as evidence for the first time in English courts. In 1903, the New York state
prisons adopted the use of fingerprints, followed later by the FBI.
The Henry system finally enabled law enforcement officials to classify and identify individual
fing-erprints. Unfortunately, the system was very cumbersome. When fingerprints came in,
detectives would have to compare them manually with the fingerprints on file for a specific
criminal (that's if the person even had a record). The process would take hours or even days and
didn't always produce a match. By the 1970s, computers were in existence, and the FBI knew it
had to automate the process of classifying, searching for and matching fingerprints. The
Japanese National Police Agency paved the way for this automation, establishing the first
electronic fingerprint matching system in the 1980s. Their Automated Fingerprint
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Identification Systems (AFIS), eventually enabled law enforcement officials around the world
to cross-check a print with millions of fingerprint records almost instantaneously.
What are fingerprints?
Fingerprints are the tiny ridges, whorls and valley patterns on the tip of each finger. They form
from pressure on a baby's tiny, developing fingers in the womb. No two people have been
found to have the same fingerprints -- they are totally unique. There's a one in 64 billion chance
that your fingerprint will match up exactly with someone else's.
Fingerprints are even more unique than DNA, the genetic material in each of our cells.
Although identical twins can share the same DNA -- or at least most of it -- they can't have the
same fingerprints.
Fingerprints are made of an arrangement of ridges, called friction ridges. Each ridge contains
pores, which are attached to sweat glands under the skin. You leave fingerprints on glasses,
tables and just about anything else you touch because of this sweat.
All of the ridges of fingerprints form patterns called loops, whorls or arches:
•
•
•
Loops begin on one side of the finger, curve around or upward, and exit the other side.
There are two types of loops: Radial loops slope toward the thumb, while ulnar loops
slope toward the little finger.
Whorls form a circular or spiral pattern.
Arches slope upward and then down, like very narrow mountains.
These three basic fingerprint types can be further separated into 8 specific types, as pictured
below (as viewed by LOOKING AT A PICTURE OF THE FINGER):
43
Take special care in classifying radial and ulnar loops: in particular, be sure you understand
whether you are looking at a PICTURE OF THE FINGER or a FINERPRINT (a transferred
print). This point will be further clarified in class.
Scientists look at the arrangement, shape, size and number of lines in these fingerprint patterns
to distinguish one from another. They also analyze very tiny characteristics called minutiae,
which can't be seen with the naked eye. Common minutiae are shown in the diagram below:
44
45
Fingerprint Record Card
There are two types of impressions involved in taking fingerprints. The upper ten impressions
are taken individually, thumb, index, middle, ring, and little fingers of each hand. These are
referred to as the "rolled" impressions because the fingers are rolled from one side of the
fingernail to the other, in order to obtain all available ridge detail.
The impressions at the bottom of the card are taken simultaneously without rolling, printing all
of the fingers of each hand at a forty-five degree angle and then the thumbs. These are referred
to as "plain," "slapped," or "flat" impressions. The plain impressions are used to verify the
sequence and accuracy of the rolled impressions.
To get the best prints, an individual must be fingerprinted by another person; that is, an
individual should never fingerprint himself/herself!
Procedure
1. Obtain a Ten Card but do not glue it into your journal.
2. Fingers to be printed must be clean and dry. If necessary, wash your hands with soap and
water and thoroughly dry them.
3. Fold the ten card along the line between the right-hand fingers and the left-hand fingers.
4. Place the fingerprint card on the front edge of the table.
5. The individual being fingerprinted should stand in front of and at a forearm's length from the
ten card. The individual should stand to the right and rear of the person taking the
fingerprints.
6. Encourage the individual being fingerprinted to relax. Ask them to look at some distant
object to distract them from what you are doing.
7. Grasp the individual's right hand at the base of the thumb with your right hand. Cup your
hand over the individual's fingers, tucking under those fingers not being printed. Guide the
finger being printed with your left hand.
8. Roll the finger on the inking pad so that the entire fingerprint pattern area is evenly covered
with ink. The ink should cover from one edge of the nail to the other and from the crease of
the first joint to the tip of the finger. Using the right amount of ink is of vital importance.
Too little ink and the impression will be too light. Too much ink and the fine details will run
together.
9. In taking the rolled impression, the side of the
bulb of the finger is placed upon the paper
fingerprint card and the finger is rolled to the
other side until it faces the opposite direction.
Care should be exercised so the bulb of each finger
is rolled evenly from tip to below the first joint.
Generally, the weight of the finger is all the
pressure needed to clearly record the fingerprint.
46
10. Roll each finger from nail to nail in the appropriate space taking care to lift each finger up
and away after rolling, to avoid smudging.
11. When you are finished fingerprinting the right hand, fold the card so that the squares for
printing the left hand are closest to the table.
12. Repeat the printing process for the left hand.
13. Plain impressions are printed last, at the bottom of the card. The
technician re-inks each finger then simultaneously presses the
individual's four fingers (on the right hand), keeping the fingers
together, on the surface of the fingerprint card or the
fingerprinting device at a forty-five degree angle in order to
capture all four fingers in the allotted space. Repeat this process
for the left hand.
14. Print both thumbs simultaneously in the plain impression thumb
blocks (to ensure that they are in the proper spaces).
15. The individual being fingerprinted can now wash his/her hands
again. Then, fill in the information at the top of the ten card and
place it (but don’t glue it!) into your journal.
Conclusions
1. Identify each of your 10 fingers as one of the 8 patterns.
2. A tally of the frequency of each pattern type within this classroom. Record the frequency
of your prints on that tally.
3. Once everybody in the class has recorded their frequency, calculate the statistical likelihood
of
a) each single type of fingerprint being found in the classroom
b) each single type of fingerprint being found on any single person within the classroom.
4. Rank the eight pattern types in term of their statistical chance of being found in our
classroom.
5. If police suspected someone in our class of committing a crime, which print type would be
most valuable in narrowing down the number of suspects? Which print type would be least
valuable?
47
Individualizing Fingerprints
When humans touch objects with their hands they often leave behind evidence in the form of
fingerprints. Sweat and oil collect on these ridges and are transferred to objects, leaving behind a
copy of the friction ridge pattern. Everybody’s friction ridge pattern is unique, which is why
forensic scientists use them to identify individuals. Although each person’s fingerprints are
distinct, they do follow three general types; loop, whorl, and arch. Fingerprints can also be
individualized through minutiae.
In this activity, you will roll your fingerprint onto a deflated balloon. After inflating the
balloon, you will identify the minutiae of your fingerprint.
SAFETY NOTE: If you are aware of any latex allergies, please let Mrs. Damian know
before the activity begins!!
Procedure
1. Roll your finger completely in the ink pad
2. Place finger, flatly and firmly on the deflated balloon. Once a fingerprint is on the
balloon, remove finger without smudging the ink.
3. Blow up the balloon and tie it.
4. Examine the ridges of your fingerprint once it has expanded with the balloon; using a
magnifying glass sometimes makes examining the minutiae easier.
5. Using a marker, write on the balloon:
a. Your name
b. Which hand and finger you printed
c. Identify the print as one of the 8 fingerprint types
d. Identify at least 13 points of minutiae, including at least 5 different minutiae.
6. When you are done, deflate your balloon by gently poking a hole in it, cut out the
fingerprint portion of it, and tape that portion into your journal.
Conclusions
1. Which minutiae are MOST common on the print you took?
2. Were there any minutiae that you could not find in your print?
3. Compare your print with other students in the class. Summarize which minutiae
seemed to be most prevalent and least prevalent.
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Fingerprint Homework
Directions: In the enlarged print shown below, identify the type of ridge pattern. Then,
identify the location of 16 points of minutiae. The first 7 points of minutiae have been
named already – you only need to circle and example of each and label it with the
appropriate number. The remaining 9 points can be any example of minutiae – identify them
by name, circling and labeling each on the print.
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Directions: From the 20 prints shown below, match the ones that are made by the same
finger. In some cases, one print may appear two or three times. Some will not match. For
example, you might say “B and D match” and “A has no match”. Write your answers in the
spaces below. Then, circle at least two specific minuteau that support each match you make.
A _________
F _________
K _________
P _________
B _________
G _________
L _________
Q _________
C _________
H _________
M _________
R _________
D _________
I _________
N _________
S _________
E _________
J _________
O _________
T _________
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Visualizing Fingerprints
One of the main tasks of the crime scene investigator is to recover fingerprint impressions in
order that a positive identification can be ascertained. Since no two individuals have the same
fingerprints and these remain unaltered during the course of a person's lifetime, the main type
of physical evidence that can be extracted from a crime scene are fingerprints.
There are three distinct types of fingerprint impressions that can be recovered from a crime
scene or a scene of interest for investigators looking for some clues as to a missing person, or
for other identification purposes. These categories are as follows:
PATENT or VISIBLE PRINTS - are prints that occur when a foreign substance on the skin of
a finger comes in contact with the smooth surface of another object. These prints leave a
distinct ridge impression that is visible with the naked eye without technological enhancement
of any kind. The tried and true "blood on his hands" evidence is an example of patent prints
recovered from a crime scene or scene of interest to investigators. These foreign substances
contain dust particles that adhere to the ridges of the fingers and are easily identifiable when
left on an object. Visible prints are preserved either by collecting and bagging them, or by
photographing them.
PLASTIC PRINTS - are visible, impressed prints that occur when a finger touches a soft,
malleable surface resulting in an indentation. Some surfaces that may contain this type of
fingerprint are those that are freshly painted or coated, or those that contain wax, gum, blood or
any other substance that will soften when hand held and then retain the finger ridge
impressions. These prints require no enhancement in order to be viewed, because they are
impressed onto an object and are easily observable. Plastic prints cannot by dusted or lifted –
they can only be photographed.
LATENT PRINTS - are fingerprint impressions secreted in a surface or an object and are
usually invisible to the naked eye. These prints are the result of perspiration that is derived
from sweat pores found in the ridges of fingers. When fingers touch other body parts, moisture,
oil and grease adhere to the ridges so that when the fingers touch an object, such as a lamp, a
film of these substances may be transferred to that object. The impression left on the object
leaves a distinct outline of the ridges of that finger. These fingerprints must be enhanced upon
collection and, because they serve as a means of identifying the source of the print, they have
proven to be extremely valuable over the years in the identification of its source. Latent prints
that have been dusted can be preserved by lifting; if, however, the print is visualized through
chemical means (eg, fuming), it cannot be lifted. Preserve fumed prints by photographing
them.
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Visualizing Plastic Prints
Visualizing Latent Prints - Dusting
In this activity, you will visualize plastic prints and you will lift latent prints through dusting
with magnetic powder. Before you get started, you need to create some specimens to be tested.
We will be using magnetic powders to develop the latent prints instead of the more traditional
talc powder and brush. The use of magnetic latent print powder and applicators permits the user
to develop latent prints on any non-ferrous surface without the risk of latent print ridge
destruction because the powder forms the brush. Therefore, excessive force during the
application of powder is eliminated.
Creating Prints
1. Choose three items made out of nonporous substances, such as a glass, metal or tile.
2. Use a soft cloth to polish the item clean, removing any contamination. You will cheat a little
to make sure the latent prints are as good as possible--for your first attempt, you may find it
difficult enough to get usable prints even under perfect conditions--by rubbing your fingers
against your nose or forehead and then carefully pressing the finger into contact with the
surface, making sure not to smear the prints.
3. Use either your thumb, your index finger, or your middle finger of either your left or right
hand to make a print on each of three items (you can use different fingers on each of the
three items). To make a print, gently but quickly press your finger onto the surface of the
material. Do not roll your finger back and forth, as that will smudge the print.
4. Be sure to avoid touching any part of the surface other than the edge as you place your three
items into three separate evidence bags.
5. Create a plastic print in the clay. Place it in an evidence bag.
6. Record in our journal the four items you printed, including which hand and finger you used
to print each item.
7. Exchange your evidence AND your ten card with someone in the class who is NOT in your
group.
Procedure – Latent Prints
1. Record in your journal whose ten card/evidence you are using.
2. Place a clean sheet of paper underneath your work surface to catch extraneous pieces of
magnetic powder.
3. Put one of the pieces of evidence on the paper. Since you are unsure which part of the
object has been printed, it may take several tries to locate the print. Remember – it could
be on either side, so if you don’t see a print developing, try turning the object over.
4. Push the sliding metal extension to its lowest position in the body of the magnetic wand.
5. Hold the wand over the open bottle of magnetic latent print powder.
6. Remove the wand from the powder and note that the powder adheres to the wand, forming
brush. If there is an excess of powder on the wand, tap it gently.
7. Gently “paint” the surface you want to visualize with powder until the print becomes
visible. The key to proper print development is to use a small amount of powder and a
delicate touch.
8. When finished, hold the wand over the bottle of powder and pull the slide extension upward
to release the powder.
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9. Photograph the latent prints with a camera or a Dinoscope. Be sure to get the entire print in
the shot (use the Dinoscope stand if you need to.
10. Once you have photographed the prints, the developed prints should be lifted with tape:
a. Attach the tape to the base of the print.
b. Holding the tape taut and beginning at the base of the print, gently begin pressing the
tape down as you move upward and beyond the print. This should eliminate air bubbles
and smearing.
c. Gently pull back the tape, lift the print, and place it on an index card. Describe where
the print came from (which piece of evidence) and how it was developed on the index
card.
d. Glue the index card into your journal.
11. Clean up the working area by moving the wand over the surface to pick up excess powder.
EACH member of your team should lift at least two prints! So – if you ruin more than one of
the latent prints prepared for you, tell Mrs. Damian so that she can get you another one.
Procedure – Plastic Prints
1. Photograph the plastic print with a camera or a Dinoscope, being sure the lighting is
sufficient to visualize the print as much as possible. Print the photo and glue it in your
journal.
Conclusions
Do NOT write on the ten card!!!
1. Use the photos and/or lifted prints, along with the provided ten card, to identify which finger
was used to print the objects. Be sure to indicate right or left hand as well as which finger
matched the print.
2. Prepare a photo comparison of the best match you made. In your written description,
indicate the person and finger you believe match. Justify your conclusions by identifying the
pattern of the print (type of arch, loop, etc.) as well as identifying at least 5 points of
minutiae (circle and identify each on the photos you took).
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Visualizing Latent Prints - Fuming
Dusting for latent prints is a skill that, if not perfected, can often result in prints that are damaged
beyond recognition. Additionally, many soft, porous surfaces such as paper, Styrofoam cups, and
leather do not dust well. Fortunately, chemical alternatives to dusting exist, and some – including
the fuming method you will do – are fairly simple, fast, and effective.
1. Retrieve your ten card from whomever you gave it to during the last lab.
2. You will be working in groups of three for this activity. Make sure each member of your
group has their 10 card.
3. Examine the 10 cards to find a single fingerprint that is somewhat common (loops are
usually good). Use that finger (of only ONE member of your group) to print each of your
objects.
4. Switch your evidence and all three 10 cards with another group. Your goal will be to
identify the person and the finger used to print the other group’s objects.
Safety Caution: Do not get superglue on your skin and do not breath the fumes. Keep your
face away from the top of the developing chamber when you slowly remove the lid.
Procedure
5. In the hood, make sure there is a chamber with a hot coffee cup warmer available.
6. Stand up your evidence or hang it inside the fuming chamber in a manner allowing
maximum exposure to fumes. Lean cans in corners, hang baggies by a paper clip, etc.
7. Place a small beaker of hot water inside the chamber to add humidity to the air. (Use the
microwave oven in the stock room to heat the water up.)
8. There should be a scrap of foil on the coffee cup warmer. Put liquid superglue on that foil
(enough to cover a nickel).
9. Place a cover on your chamber and leave it for about 15 minutes.
10. After 15 minutes, shut off the heat, open the chamber and check your prints. If any of the
print are visible, the evidence is properly processed and ready to examine (it is possible that
not all of the prints will be visible). If none of the prints turned at least a little white, add
some more superglue, close the chamber and fume for ten more minutes.
11. Photograph the developed prints with a camera or a Dinoscope. Print the photos and glue
them in your journal.
Conclusions
1. Use the photos along with the provided ten card to identify which person and finger was
used to print the objects. Be sure to indicate right or left hand as well as which finger
matched the print.
2. Prepare a photo comparison of the best match you made. In your written description,
indicate the person and finger you believe match. Justify your conclusions by identifying the
type of print (type of arch, loop, etc.) as well as identifying the type of print, and identify at
least 5 points of minutiae (circle and identify each on the photos you took).
54
Final Conclusions for Fingerprinting Unit
1. What type of fingerprint (plastic, visible, or latent) would likely be found in, on, or by
means of the following materials?
a. blood
b. mud
c. wood tabletop
d. windowpane
e. a chunk of Romano cheese
f. chalk
g. skin
h. plastic bag
i. fudge
j. dust
k. newspaper
l. leather jacket
m. gun barrel
n. snow
2. What would be the best way to visualize latent prints on the following materials (dusting or
chemical developing)?
a. matchbook cover
b. toilet seat
c. doorknob
d. cigarette butt
e. broken bottle
f. lightbulb
3. Consider the following case study:
A burglar approached a house from the backyard late one evening, knowing that the owners
were not at home. He tried and failed to pry open several windows behind a flowerbed.
Finally, he broke a windowpane with the old pry bar, reached through, scraping his shirt
sleeve against a jagged shard of glass, and turned the latch. He raised the window, not
thinking about how soft the putty was when his fingers touched the glass. He climbed in
over the sill and was promptly bitten in the leg by the owner’s dog, provoking a sharp blow
to the dog’s head with the pry bar. The burglar then went upstairs to the bedrooms to collect
jewelry. When he was satisfied with his haul, he unlatched the back door and disappeared
into the night.
a.
b.
c.
d.
Make a list of evidence that could be used to link a suspect to the burglary.
What would be the best way of developing the latent fingerprints at each area?
Would the fingerprint evidence be direct or circumstantial evidence? Explain why.
Would the fingerprint evidence be class or individualized evidence? Explain why.
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