Lesson 2 Fingerprints
Pre-Lesson Reading
1.
Fingerprint Principles:
According to criminal investigators, the use of fingerprint follows 3 fundamental
principles:
a. A fingerprint is an individual characteristics because no two fingers have
yet been found to possess identical ridge characteristics.
b. A fingerprint remains unchanged during an individual’s lifetime.
c. Fingerprints have general ridge patterns that permit them to be
systematically classified.
2.
Origin of fingerprint:
a.
3.
b.
Take a look at your fingertip. You’ll see small ridges made of skin. The
ridges have a purpose. They help you get a better grip on stuff you pick
up.
The ridges develop in the womb and remain the same throughout life,
barring some sort of scarring or trauma to the deep skin layer. Although
people grow and increase in size, the ridges became permanent and fixed
in their patterns from about 17 weeks of embryonic development, ridge
c.
patterns do not change like other parts of our bodies.
When the finger touches a surface, perspiration and oils are transferred
onto that surface, leaving a pattern called fingerprints.
All fingerprints are classified into three categories on the basis of their general
patterns:
a. Arches
 Ridges enter on one side and exit on the other side.
 Approximately 6% of people exhibit this pattern.
b.
Loops
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c.

Ridges enter on one side and exit on the SAME side.

Approximately 60% of people exhibit this pattern.
Whorls


4.
Types of fingerprint evidence:
a.
b.
c.
5.
Consists of circles, spirals.
Approximately 34% of people exhibit this pattern.
Patent prints
These are clearly visible. They’re made when you touch something like
paint or blood and then touch other surfaces.
Latent prints
They’re formed when you touch something and the oil and sweat on your
hand leaves a print. Latent prints are mostly invisible to the naked eye.
Fingerprinting dust makes them visible.
Physical prints
These are made when you touch something like gum that leaves a clear
impression of your prints.
Three common methods of latent print enhancement:
a. Lifting powder Application

Work bests upon smooth solid surface, e.g. walls, glass, knife

Fingerprint powders are colored, fluorescent, or magnetic materials
that are very finely ground and are brushed lightly over a suspected
print to produce contrast to the background. These powders typically
are available in black, white and other colors, including metallic.
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
b.
Once the lifting powder has been successfully applied a fingerprint is
then “lifted” using a wide piece of clear smooth tape.
Iodine Fumigation

Work bests upon light-colored light weight/low density objects, e.g.
paper, fabrics

A small amount of iodine is placed at bottom of a glass chamber. The
object bearing the suspected latent prints is then suspended from the
top of the chamber. The chamber is then sealed and chemical
reaction occurs. The latent fingerprints become dark brown in colour
and photograph of the fingerprint will be taken.
WARNING: Iodine is irritating to skin and eyes. Do not breathe in iodine
vapours.
c.
Cryanoacrylate Fumigation



Cryanoacrylate is a very strong glue. It has tendency to stick to the
body oil residue found in fingerprint.
Work bests upon dark-colored dense objects, e.g. guns, knife handles.
When Cryanoacrylate begins to react with the body oil residue in a
fingerprint, it leaves behind a whitish-grey film which is visible to the
human eye. Photograph of the fingerprint will be taken.
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Lesson 2 Fingerprints
Worksheet 2.1
1.
Classify each of the following prints as loop, whorl or arch.
a.
2.
Fingerprint Basics
Arch
b.
loop
c.
____whorl ___
While searching a murder scene, you believe the following items may contain
latent fingerprints. Indicate whether prints on each item should be developed
using fingerprint powder or chemicals.
a. A leather sofa
chemicals
b.
A mirror
powder
c.
A painted wooden knife handle
powder
d.
Blood-soaked newspapers
chemicals
3.
Fingerprints that deposited on a surface when oils and sweat are excreted from
pores on the friction ridges are called ____ Latent _______ fingerprints.
4.
The most common fingerprint pattern is the ___ Loop _______ .
5.
True or False
a. The individuality of a fingerprint is determined by its pattern.
F
b.
Fingerprints cannot be changed during a person’s lifetime.
T
c.
Arches have type lines, deltas and cores.
F
d.
The identical twins have the same fingerprints.
F
e.
Computerised fingerprint search systems match prints by
comparing the positions of bifurcations and ridge endings.
T
f.
A fingerprint left by a person with soiled or stained fingertips is
called a latent print.
F
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Lesson 2 Fingerprints
Worksheet 2.2
Practice the identification skills
e.g. fork
Figure 1 ______________________________
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Instruction:
1. Examine the fingerprint (Figure 1) with a magnifying glass if necessary.
2. To which class does the fingerprint pattern belongs? Write down your answer..
3. Use Table 1 to help identify fingerprint ridgeline details. Locate and label at
least 8 positions of ridgeline details in Figure 1.
Table 1
Fingerprint ridge details
Fork
Double Fork
Triple Fork
Delta
Dot
Bridge
Hook
Eye
Short Ridge
Ending Ridge
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Suggested Answers
dot
fork
ending ridge
hook
eye
ending ridge
double hook
bridge
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Lesson 2 Fingerprints
Worksheet 2.3
Make a fingerprint
Apparatus and Materials:
(per group)
2 2B pencils
2 pieces of white paper
1 bottle of fine iron powder
1 adhesive tape
1 handkerchief
4 microscope slides
1 magnifying glass
Procedures:
Part 1
Patent fingerprinting
1. Rub a 2B pencil over a piece of white paper until it is covered with graphite.
2. Rub your index finger against your nose or forehead and place the finger at the
center of the microscope slide.
3. Press and roll your index finger firmly on the graphite pad and then press the
4.
5.
finger on the tape thoroughly.
Place the fingerprint on the worksheet.
Repeat step 2 to 4 for another index finger.
Part 2
Latent Fingerprinting
6. Use a handkerchief to wipe a microscope slide free of any stray fingerprints.
Handle the slide only by the edges.
7. Rub your index finger against your nose or forehead and place the finger at the
center of the microscope slide.
8. Sprinkle the iron powder onto the edge of the print.
9. Lightly shake the slide to apply a thin coating of iron powder onto the latent
print.
10. As the print becomes visible, you should shake the slide lightly until there is no
excess iron powder on the slide.
11. To lift the fingerprint from the slide, you should position the untouched portion
of the tape above the imaged fingerprint and smooth the tape over the developed
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print.
12. Place the fingerprint on the worksheet.
13. Repeat step 7 to 13 for the rest of your fingers.
Part 3
Statistics
14. Identify the pattern of each your fingerprint.
15. Write down the name of pattern under each fingerprint.
16. Count the numbers of each pattern.
Part 4
Identify the ridgeline details
17. Choose the fingerprint with best resolution among all your fingerprints.
18. Examine the fingerprint with magnifying glass.
19. Use Table 1 of Worksheet 2.2 to help identify fingerprint ridgeline details.
Results:
1. Direct prints of your fingers
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2.
Latent prints of your thumb and index finger
3.
Among all your fingerprints, the numbers of each pattern are as follows:
No. of Arches： __________
No. of Loops：
No. of Whorls：
__________
__________
Do all your fingerprints have the same pattern? ________________
4.
List out the names of ridgeline details you can identify. Count the frequency of
each ridgeline detail.
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Group discussions
1.
Count the number of patterns of all fingerprints among your group. What is
population percentage of each pattern? Show your calculations.
2.
Which pattern is most common among your group members?
3.
Which colour is the most popular color for fingerprint powder? Why?
Suggested answers:
Black is the most popular colour because it creates the sharpest contrast on a white
card, commonly used for filing and recording fingerprints. This provides a uniform
medium for the comparison of black ridges of the questioned print to the black inked
ridges of the known print.
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Lesson 2 Fingerprints
Worksheet 2.4
Try out the steps in analyzing and comparing fingerprints
Case Profile
A suspect was arrested in a burglary case. When the suspect was
fingerprinted, the desk sergeant noticed something very unusual – his
fingerprints somehow had been altered. The suspect admitted that he had
peeled off the skin from one of his thumbs and transplanted it onto another
thumb. The suspect even claimed that “I have new thumbprints. I am a
clean person.”
Furthermore, the police have recovered an excellent latent thumbprint from an
unsolved burglary case 3 years ago. There are some indications that these 2
cases may be related.
The recovered print and the suspect’s new thumbprints are provided for your analysis.
Can a match be made between the direct thumbprints from the suspect and the latent
thumbprint found at the crime scene? Imagine you are fingerprint examiner and you
need to evaluate the presented evidence, reach conclusions and provide findings in a
report to the law enforcement authorities and the court.
Known left thumbprint from
suspect
Known right thumbprint from suspect
The five steps in analysing and comparing
fingerprints:
Step 1: Identify the general type of the central
area of the fingerprint.
Step 2: Match fingerprint ridgeline details.
Step 3: Compare the unknown print and the
known print, point by point, feature by
feature, to see if they match.
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Recovered print from burglary
Step 4: Evaluate whether the unknown print
scene
matches the known print or not.
Step 5: A second examiner verifies the results.
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Report
Known left thumbprint from suspect
Known right thumbprint
from suspect
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Recovered print from burglary scene
Can the suspect be identified? Summarise your findings and report conclusions to
law enforcement authorities and the court.
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Answers
Known right thumbprint from suspect
Known left thumbprint from suspect
Recovered print from robbery store.
The area of surgical transfer is oultlined in blue. Matching areas correspond to the
dots.
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Hints:
1. Look over the direct fingerprints and then look at the latent thumbprint found at
the burglary. Observe any areas on the direct thumbprint that show disrupted,
unusual ridgeline patterns (e.g., altered, upside down or misaligned). Use a
colour pen to circle the unusual area.
2. Look at the fingerprints carefully with a magnifying glass. Do you find points of
similarity? Can any ridgeline details in latent thumbprint be matched to either of
the direct fingerprints? If you spot any possible matches, circle the features in
red on the fingerprints and number the features correspondingly.
3. Write down your conclusions.
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Lesson 2 Fingerprints
Follow-up Activity
1.
Case study: Fingerprints on 2004 Madrid train bomb bag traced to Algerian
“Fingerprints found in a plastic bag containing detonators of the kind used in
the March 11 Madrid train bombings were identified as belonging to an
Algerian national, police said Thursday evening..”.
Read the following or related articles and discuss what’s wrong with FBI.
http://onin.com/fp/FBI_LPOU_SLIDES_IAI_2008_AUG_18.pdf
http://www.usdoj.gov/oig/special/s0601/PDF_list.htm
http://www.usatoday.com/news/world/2004-05-20-algerian-madrid_x.htm
http://www.foxnews.com/wires/2006Nov29/0,4670,SpainBombingsFBI,00.
html
http://www.usatoday.com/news/world/2004-05-20-algerian-madrid_x.htm
2.
The following articles help you learn more about the history of fingerprinting
a. http://www.criminaljustice.state.ny.us/ojis/history/fp_sys.htm
b. http://www.onin.com/fp/fphistory.html
3.
If you want to learn more about the latest development in fingerprinting, you
may visit the following website.
http://onin.com/fp/
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