JS 111:
I. Intro to Physical Evidence
II. Detection, Collection, Presumptive testing and
Preservation of Biological Evidence
I.
Pre-class activities
A. Group Quiz
B. Announcements and Assignments
II. Intro to Physical Evidence- Learning Objectives
A. Define Locard’s Exchange Principal
B. Define class vs. individual characteristics
C. Define Comparison vs. Identification
III. Detection, Collection and Presumptive Learning Objectives
A. List the sources of Biological Evidence
B. Discuss presumptive tests utilized on biological evidence
C. Discuss proper collection of biological evidence
D. Understanding how to avoid contamination
E. Understanding how to detect and monitor for contamination
Quiz 1
Assignments (posted on my sitehttp://www.sjsu.edu/people/steven.lee/
Due Today 07 Feb 11
1) Plagiarism Tutorial
2) Read Chapter 1, Chapter 2 and Chapter 3 in Butler 2010
(Chapter 1 and Chapter 2 in Butler 2005) Inman and
Rudin- Chapters 3 and 5 (These chapters will be posted on
the web site by weds 2 Feb)
3) Review History of forensic DNA
http://www.dna.gov/basics/analysishistory/
4) Study for a quiz- Review the Powerpoint on line, notes
from 31 Jan and the above assignments
Assignments Due 14 Feb
• Special collection guidelines for Biological Evidence
• Read the following article:
http://www.cci.ca.gov/Reference/biosmpl.pdf
• Write a 300 word summary and 3 questions and 3 answers
• Re read Ch 2-3 Butler and Inman and Rudin 3 and 5 (will
post this week)
• Study for quiz
• Extra Credit- Find a news, magazine or journal article on
regarding the proper collection/storage of biological
evidence from 2011. – Write a 500 word summary and 3
questions and 3 answers- Bring in hard copy by 14 Feb.
• See SJSU events page for Dr. Bond lecture for extra credit
point for attending (be sure to sign in) and summarizing
the lecture in 500 words
Bond Lecture 10 Feb
• Event Description
‘Fingerprints Forever:’ Visualizing Fingerprint Corrosion
of Metals
• Guest Speaker:
• Dr. John Bond,
Research Fellow
University of Leicester, England
Scientific Support Unit Mgr for Northamptonshire Police
• 10th February 2011
• San José State University – Engineering 285/287 Map,
directions and parking- http://www.sjsu.edu/map/
Lecture and Hands-on demo: 11:am-12:30 pm
Lunch: 12:30 pm-2 pm
Detailed Seminar and Discussion: 2:30 pm -3:30 pm
Dinner (Optional) 5 pm-7 pm
Acknowlegements
–
–
–
–
–
Butler 2005 and 2010
Saferstein R. 2004. Chapter 3
Gary Sims- Personal communication 2003.Powerpoint slides on contamination
http://www.cci.ca.gov/Reference/peb/peb.htm
l
Jeremiah Garrido 2003- Slides on
presumptive testing- Santa Clara County
Crime Laboratory
Small Group Exercise 1
What samples provide DNA?
• DNA can be typed from a number of different types
of samples and sources. You have a missing person
and there are no known blood samples available as a
reference.
• In your small groups, list all types of samples you
believe will provide DNA typing results that may
provide a reference for the missing person. Start with
the ones with the highest probability of typing.
• You have 10 minutes to complete, review and edit
your lists
• Be sure that all members of your group sign and print
their names and submit the list
DNA Chant
The subject of the course today (me)
Is simply stated DNA
(you)
Sugar-Phosphate backbone chains
(me)
Hold the base pairs heres their names (you)
Chorus:
AT(me)- AT(you)
GC(me)- GC(you)
ATGC, ATGC (together)
RFLP holy grail
Put bad guys away in jail
PCR can lend a hand
Amplifying those weak bands
---------------->Chorus
Blood, saliva, semen too,
Can be used as crucial clues
Fingernails and skin and hair
DNA is everywhere
--------------->Chorus
Locard’s Exchange Principle
"Every Contact Leaves a Trace“
Or Contact results in cross transfer
The value of trace (or contact) forensic evidence was
first recognized by Edmund Locard in 1910. He was
the director of the very first crime laboratory in
existence, located in Lyon, France.
The Locard’s Exchange Principle states that "with contact between two
items, there will be an exchange." For example, burglars will leave traces
of their presence behind and will also take traces with them. They may
leave hairs from their body or fibers from their clothing behind and they
may take carpet fibers away with them.
Source: http://www.virtualsciencefair.org/2004/fren4j0/public_html/trace_evidence.htm
What is Physical Evidence?
• Anything that can show that a crime has been committed
or that can be used to show a connection.
scene
suspect
Physical
evidence
victim
Locard’s Exchange Principle- contact results in a crosstransfer of evidence
Physical Evidence may also…
•
•
•
•
•
Connect one crime to another crime
Identify unknown/missing persons
Exonerate or free the innocent
Support statements (testimony)
Convince a suspect to confess if they know you “got the
goods on them”
• Provide leads for a case
A few examples of common types of Physical evidence
•
•
•
•
•
•
•
Fingerprints, latent and visible
Blood, saliva, hair, human or animal
Paint
Firearms and ammunition
Glass-particles, fragments
Impressions- shoeprints, bite marks
Tool marks-object containing
impression of another object
Introduction to Physical
Evidence
The Value of Physical Evidence
Recognize, Collect, & Preserve
The roles of Physical Evidence:
1. Reconstruct the Crime Scene & Sequence of
Events
2. Determine whether or not a crime occurred.
3. Link an individual with another or with a crime
scene
4. Provide Investigative Leads to Investigators.
5. Provide facts to a jury which may assist in the
determination of the guilt or innocence of an
accused.
6. Provide evidence to link serial homicide or rape
case.
Advantages of Physical
Evidence
• Provides a tangible object for the jury to see
• Can be taken into the jury room
• The defendant cannot distort the physical
evidence.
• Some cases cannot be solved without the
physical evidence
• Physical evidence is not subject to memory loss
• The defendant can have the evidence tested by
an independent expert.
Evidence- anything that can be used to
determine whether a crime has been committed.
Materials collected and scientifically
analyzed to determine the nature
and circumstances of a crime.
Direct-establishes a fact (eyewitness)
Circumstantial- provides an inference about
what happened (more reliable than direct)
COMPARISON
IDENTIFICATION
•To determine the physical or
chemical identity of a substance
with as near absolute certainty
as existing analytical techniques
will permit. What is it?
•Subjecting a suspect specimen
and a standard (reference)
specimen to the same tests and
examinations for the purpose of
determining whether or not
there is a common origin.
Does it Match?
It is imperative to conduct a thorough collection and scientific
evaluation of physical evidence for all criminal investigations.
Physical evidence can be used to link an individual
to a crime or to exonerate a person from suspicion.
• Common Types of Physical Evidence:
(Reconstructive vs. Associative)
–
–
–
–
–
–
–
–
–
–
Blood, Semen, and Saliva
(B)
Documents (P)
Drugs (P)
Explosives (P)
Fibers (P)
Fingerprints (P)
Firearms and Ammunition (P)
Glass (P)
Hair (B)
Tool Marks (P)
- Impressions (P)
- Organs & Body Fluids (B)
- Paint (P)
- Petroleum Products (P)
- Plastic Bags (P)
-Plastic, rubber, & polymers
- Powder Residues (P)
- Serial Numbers (P)
- Soil & Minerals (P)
- Vehicle Lights (P)
-Wood and plant matter (B)
Physical Evidence
Characteristics
• Class Characteristics
– Properties of evidence
that can only be
associated with a group
and never with a single
source.
– The “product rule” is
often used to calculate the
overall frequency of an
occurrence in a
population. (multiply the
frequencies of
independently occurring
genetic markers)
• Individual
Characteristics
– Properties of evidence
that can be attributed to a
common source with an
extremely high degree of
certainty or probability.
The practical and personal experience of the examiner supports
or negates the significance of these evidence characteristics.
Identifying Physical Evidence
• Presumptive Tests
– Identify suspect
evidence (class)
– Cheaper
– Faster
– Can be done at crime
scene
– Less training needed
– Help focus
investigation
• Confirmatory Tests
– Can lead to individual
classifications
– Costly
– Time consuming
– Typically done in the lab
– More exact procedure
– Match a suspect to a
crime
Sources of Biological Evidence
Material
Blood and blood stains
Semen and semen stains
Bones
Teeth
Hair with root
Hair shaft
Saliva (with nucleated cells)
Urine
Feces
Debris from fingernails
Muscle tissue
Cigarette butts
Postage stamps
Envelope sealing flaps
Dandruff
Fingerprints
Personal Items: Razor blade,
chewing gum, wrist watch, ear wax,
toothbrush
Reference
Budowle 1995
Budowle 1995
Gill 1994
Alvarez 1996
Higuchi 1988
Wilson 1995
Sweet 1997
Benecke 1996
Hopwood 1996
Wiegand 1993
Hochmeister 1998a
Hochmeister 1991
Hopkins 1994
Word 1997
Herber 1998
Van Oorschot 1997
Tahir 1996
Steps in Forensic DNA typing
Evaluation- Is it there?
(Figure 6.1 Rudin and Inman 2001)
1.
Start with biological sample
2.
Screen- blood? Semen? Saliva, human?
Extraction- Get and clean DNA
3.
Open cells  Get DNA
4.
Methods to get DNA and purify DNA
Quantify- Determine quality and quantity?
5.
QuantifyHow good and how much did you get?
Type to determine and compare alleles
6. RFLP vs PCR
7. Determine alleles and compare DNA types
Or alleles present in samples and references
Interpretation of Results
Real Forensic Biologists must first screen
evidence for biological fluids before DNA testing:
The “Art” of Forensic Science
• What are they?
• Forensic Value ?
– Cells
• Most commonly
analyzed
BODY
FLUIDS
Cell Types
Blood
White
Blood Cells
Semen
Spermatozoa
Saliva
Skin Cell
Blood as Physical Evidence
•
Occurrence of a blood stain in a certain place
on an item may substantiate an account of a crime
• Bloodstain Pattern Interpretation:
Shape, position, size or intensity of a bloodstain
may support a particular sequence of events
• DNA typing analysis can be used to eliminate
whole groups of people as suspects
Blood spatter patterns may be used to
determine the position of the source
Where are the 10-80o drops coming from?
Pointed end of a Bloodstain
points in the direction of travel
The Nature of Blood
• Blood- A complex mixture made of cells,
enzymes, proteins and inorganic
substances
– Liquid portion (55%) : Water
– Solid portion (45%) :
• Red blood cells, white blood cells,
platelets
• Serum: Liquid containing antibodies
that separates from blood when a clot
forms
Nature of Blood: Function
• Red blood cells (RBC):
– Transports oxygen from lungs to body tissues
and in turn removes carbon dioxide by taking it
to the lungs.
Also contain
– Antigens:
• proteins found of the surface of RBCs that
stimulates the body to produce antibodies
against it
• Grouped into systems
– ABO blood typing
• Some stains are easily detected
Neck incisions (scene)
Sometimes they
are difficult to
see with the
naked eye
Forensic
Characterization
of
Forensic
Characterization
of Bloodstains
Bloodstains
 IS THIS STAIN BLOOD?
WHAT
SPECIES?

IF HUMAN ORGIN WHO
DEPOSITED THE BLOOD?
Forensic Characterization of
Bloodstains
Three ways of characterizing a possible
bloodstain:
1. Chemical Color Tests or Crystal Test
 Based on presence of hemoglobin
2. Species Determination
 Based on Antigen-Antibody Reaction
3. Individualizing bloodstain
 DNA analysis and calculating statistics
Forensic Characterization of
Bloodstains:
Is This Blood??
• Chemical color tests
– Based on hemoglobin's
peroxidase-like activity
(Peroxidase: enzyme that oxidizes
organic compounds)
– Ex: Lab/phenolphthalein, O-tol
Crime Scene/Hemastix
– Advantage: very sensitive
– Disadvantage:
• false positive rxn
– Potato/Horseradish
– Strong oxidizers like bleach
Kastle-Meyer positive test-pink color
Tests for the presence of blood:
•
•
•
•
•
•
•
•
Phenolphthalin (Kastle-Meyer)Leucomalachite green (LMG)*Ortho-tolidine –
Luminol –
pink1:100,000
green blue1:20,000
blue positive 1:100,000
light in total darkness1:5,000,000
Tetra-methylbenzidine (TMB) – green blue1:1,000,000
Fluorescinintense green fluor1:500,000
* carcinogen
Forensic Characterization of
Bloodstains cont’d
• Luminol Test
• Produces light rather
than color
– Typically sprayed onto
suspected stains to reveal
stains & patterns
LIGHT EMISSION
STAIRCASE INTO
BASEMENT
LIGHT EMISSION
Can we say it’s
human blood?
Case Example : Homicide Scene
Natural Light
No treatment
Darkened Room
Luminol Treated