Download Intro to Forensics and Types of Evidence

Intro to Forensics and Types of
Evidence
UNIT 1
FORENSIC SCIENCE
ERLENBECK
Observation vs. Inference
—  Observation: Use one or more of your five senses to
gather information
A noting and recording of ….FACTS!!!!
¡  Give me an example
¡ 
—  Inference: A logical interpretation based upon prior
knowledge and experience.
Based upon observation
¡  Give me an example
¡ 
Note the differences…
—  In any lab exercise, you record observations, not
inferences.
—  Inferences are made when you write your conclusion
to the lab exercise.
Make 3 observations and 3 inferences about this
picture.
Eyewitness Exercise
—  Choose several people to be observers and choose
two people to be investigators.
—  Allow the observers to look at the picture for 30
seconds. The investigators should not look at the
picture.
—  After 30seconds,the investigators should begin
questioning the observers. Each Investigator should
question each observer. Then, the Investigators
should attempt to reconstruct the scene based on the
"eyewitness testimony".
Forensics is…
— Science as applied to criminal
proceedings.
— Not all forensics = DEATH.
Crime Lab History
§  First police crime lab in the world was established
in France in 1910 by Edmond Locard
§  First police crime lab in the U.S. opened in 1923 in
Los Angeles
§  The Scientific Crime Detection Lab was founded in
Evanston, Illinois in 1929
§  The first FBI crime lab opened in 1932
People of Historical Significance
Edmond Locard (1877-1966)
§  French professor
§  Considered the father of
criminalistics
§  Built the world’s first forensic
laboratory in France in 1910
§  Locard Exchange Principle
§  Whenever two objects come into
contact with each other, traces of each
are exchanged.
Crime Scene Team
§  A group of professional investigators, each trained in a variety of special
disciplines.
§  Team Members
§  First Police Officer on the scene
§  Medics (if necessary)
§  Investigator(s)
§  Medical Examiner or Representative (if necessary)
§  Photographer and/or Field Evidence Technician
§  Lab Experts
pathologist
serologist
DNA expert
toxicologist
forensic odontologist
forensic anthropologist
forensic psychologist
forensic entomologist
firearm examiner
bomb and arson expert
document and handwriting experts
fingerprint expert
Types of Crime
§  Infraction – violation not
resulting in prison: traffic,
littering
§  Misdemeanor – minor
crime: theft, assault,
possession of small amt of
drugs
§  Felony – major crime:
rape, murder, 3rd DUI
Types of Evidence
Two general types:
§ 
Testimonial—a statement made under oath; also known
as direct evidence or Prima Facie evidence
§ 
Physical—any object or material that is relevant in a
crime; also known as indirect evidence. Examples are
hair, fiber, fingerprints, documents, blood, soil, drugs, tool
marks, impressions, glass.
Reliability of Eyewitness
Factors:
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Nature of the offense and the situation in which the crime
is observed
Characteristics of the witness
Manner in which the information is retrieved
Additional factors:
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Witness’s prior relationship with the accused
Length of time between the offense and the identification
Any prior identification or failure to identify the defendant
Any prior identification of a person other than the
defendant by the eyewitness
The Facts
— In this country, it is estimated
that 75% of wrongly convicted
defendants, later cleared by
DNA evidence, were convicted
based largely on eyewitness
testimony.
Flashbulb Memories
—  Many vic)ms of crimes have something that is called a flashbulb memory —  This is a vivid recollec)on of drama)c or emo)onally charged events —  Example: Can anyone tell me what you were doing when…? You first saw or heard about September 11 ¡  Barack Obama became president ¡  Michael Jackson died
¡  Nsync broke up ¡ 
You Be the Eyewitness
—  Imagine you are at a gas station buying milk
—  A man walks in, threatens the employee at the
counter, robs the cash register, and runs out
—  The entire ordeal lasts about five seconds
—  This is the man you saw…
You Be the Eyewitness
—  The police have asked you to help them identify the
perpetrator
—  They will show you a set of pictures, and it is your
responsibility to select the picture of the man you
saw rob the gas station…
How Did You Do?
—  So, which picture did you choose?
—  And the correct answer was... #2
—  Were you right?
—  What does this tell you about eyewitness testimony?
According to Research…
—  Studies show that the longer it takes an eyewitness to
decide if the perpetrator is in a lineup, the less
confident they actually are about their decision
—  Why?
—  Eyewitnesses typically take several minutes to point
out the perpetrator because they often feel pressured
to choose the correct one
—  However, if they are truly confident, they should be
able to decide in under 10 seconds
Choosing From a Lineup
—  Research from Buckhout (1974) and Wells (1993)
indicate that an eyewitness is more likely to falsely
identify a person in a set of lineup photographs if
there is anything that separates one picture from
another
—  For example:
If one picture is larger than the others
¡  If facial features in all the photographs are not identical
¡ 
Ronald Cotton Case Study
—  hJp://www.youtube.com/watch?v=u-­‐SBTRLoPuo —  hJp://www.youtube.com/watch?
v=I4V6aoYuDcg&feature=related Value of Physical Evidence
§  Generally more reliable than testimonial
§  Can prove that a crime has been committed
§  Can corroborate or refute testimony
§  Can link a suspect with a victim or with a
crime scene
§  Can establish the identity of persons
associated with a crime
§  Can allow reconstruction of events of a
crime
Reconstruction
Physical Evidence is used to answer questions about:
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what took place
how the victim was killed
number of people involved
sequence of events
A forensic scientist will compare the questioned or
unknown sample with a sample of known origin.
https://www.youtube.com/watch?v=EPoNOpL8CvY
Types of Physical Evidence
§  Transient Evidence—temporary; easily changed
or lost; usually observed by the first officer at the
scene
§  Pattern Evidence—produced by direct contact
between a person and an object or between two
objects
§  Conditional Evidence—produced by a specific
event or action; important in crime scene
reconstruction and in determining the set of
circumstances or sequence within a particular
event
Types of Physical Evidence
§  Transfer Evidence—produced by contact
between person(s) or object(s), or between
person(s) and person(s)
§  Associative Evidence—items that may associate
a victim or suspect with a scene or each other; ie,
personal belongings
Examples of Transient Evidence
§  Odor—putrefaction, perfume, gasoline, urine,
burning, explosives, cigarette or cigar smoke
§  Temperature—surroundings, car hood, coffee,
water in a bathtub, cadaver
§  Imprints and indentations—footprints, teeth
marks in perishable foods, tire marks on certain
surfaces
§  Markings
Examples of Patter Evidence
—  Pattern Evidence—most are in the form of
imprints, indentations, striations, markings,
fractures or deposits.
Blood spatter
§  Glass fracture
§  Fire burn pattern
§  Furniture position
§  Projectile trajectory
§  Tire marks or skid marks
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§  Clothing or article
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distribution
Gun powder residue
Material damage
Body position
Tool marks
Modus operandi
Examples of Conditional Evidence
§  Light—headlight, lighting conditions
§  Smoke—color, direction of travel, density, odor
§  Fire—color and direction of the flames, speed of spread,
temperature and condition of fire
§  Location—of injuries or wounds, of bloodstains, of the
victim’s vehicle, of weapons or cartridge cases, of broken
glass
§  Vehicles—doors locked or unlocked, windows
opened or closed, radio off or on (station),
odometer mileage
§  Body—position, types of wounds; rigor, livor and
algor mortis
§  Scene—condition of furniture, doors and
windows, any disturbance or signs of a struggle
Classification of Evidence by Nature
§  Biological—blood, semen, saliva, sweat, tears, hair, bone,
tissues, urine, feces, animal material, insects, bacterial,
fungal, botanical
§  Chemical—fibers, glass, soil, gunpowder, metal, mineral,
narcotics, drugs, paper, ink, cosmetics, paint, plastic,
lubricants, fertilizer
§  Physical—fingerprints, footprints, shoe prints,
handwriting, firearms, tire marks, tool marks, typewriting
§  Miscellaneous—laundry marks, voice analysis,
polygraph, photography, stress evaluation, psycholinguistic
analysis, vehicle identification
Evidence Characteristics
§  Class—common to a group of objects or persons
§  Individual—can be identified with a particular person or a
single source
Fingerprints
Blood DNA Typing
Class vs. Individual Evidence
Which examples do you
think could be individual
evidence?
Components of Forensic Investigations
Include some or all of these seven major activities
1. Recognition—ability to distinguish important
evidence from unrelated material
§  Pattern recognition
§  Physical property observation
§  Information analysis
§  Field testing
2. Preservation—collection and proper preservation
of evidence
Components of Forensic Investigations
3. Identification—use of scientific testing
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Physical properties
Chemical properties
Morphological (structural) properties
Biological properties
Immunological properties
4. Comparison—class characteristics are
measured against those of known standards or
controls; if all measurements are equal, then the
two samples may be considered to have come
from the same source or origin.
Components of Forensic Investigations
5. Individualization—demonstrating that the
sample is unique, even among members of the
same class
6. Interpretation—gives meaning to all the
information
7. Reconstruction—reconstructs the events of the
case
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Inductive and deductive logic
Statistical data
Pattern analysis
Results of laboratory analysis
Corpus Delicti
“Body of the Crime”
—  You must prove
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¡ 
That a crime occurred
That the person charged with the crime was responsible for the crime
—  Top Reasons for Committing a Crime
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Money
Revenge
Emotion—love, hate, anger
—  Source of Evidence
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Body
Primary and/or Secondary Crime Scene
Suspect(s)
Crime Scene Investigation
—  Based on scientific method and the Locard Exhange
Principle, logic and forensic techniques.
—  Involves
Recognition
¡  Identification
¡  Individualization
¡  Reconstruction
¡ 
Processing a Crime Scene
—  Isolate and secure the scene
—  Document the scene
—  Search for evidence
—  Collect and package evidence, maintaining the chain
of custody
—  Submit evidence to the crime lab
First Officer on the Scene
—  A Assess the crime scene and assist those hurt
—  D Detain the witness
—  A Arrest the perpertrator
—  P
Protect the crime scene
—  T
Take notes
Crime Scene Survey
—  Walk-through: performed by the crime scene
investigator, the first officer, and sometimes, the lead
detective.
—  Purpose:
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Mentally prepare a reconstruction theory
Note any transient or conditional evidence that could change over
time.
Note the weather conditions
Note points of entry or exit, as well as paths of travel within the crime
scene
Record initial observations of who, what, where, when, and how
Identify special needs within the crime scene for personnel,
precautions or equipment and notify superior officers or other
agencies.
Documentation
—  Notes: date and time, description of the location,
weather and environmental conditions, description
of the crime, location of the evidence relative to other
key points, the names of all involved, modifications
that have occurred and other relevant information
—  Photography: photos of scene and surroundings,
mid-range to close-up photos with various angles or
each piece of evidence, photos as viewed by the
witness
Documentation
—  Sketches: inclusion of date, time, scale, reference
points, distance measurements, names of
investigators, victims, suspects, and a key
—  Videography: allow narration (non-subjective) to
be included.
Search Methods
—  Line or strip method: best in large, outdoor
scenes
—  Grid method: basically a double-line search;
effective, but time consuming.
—  Zone method: most effective in houses or
buildings; teams are assigned small zones for
searching.
—  Wheel or ray method: best on small, circular
crime scenes
—  Spiral method: may move inward or outward; best
used where there are no physical barriers
Crime Scene Sketch
Collecting & Packing Evidence
§  One individual should be designated as the evidence
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collector to ensure that the evidence is collected,
packaged, marked, sealed, and preserved in a
consistent manner
Each item must be placed in a separate container,
sealed, and labeled
Most fragile is collected and packaged first
Different types of evidence require specific or special
collection and packaging techniques
The body is the property of the coroner or medical
examiner. The collection of evidence on the body is
done by that department
Packing
—  Most items should be packaged
in a primary container and then
placed inside a secondary one.
These are then placed inside
other containers such as paper
bags, plastic bags, canisters,
packets and envelopes
depending on the type and size
of the evidence.
Chain of Custody
There must be a written record of all people
who have had possession of an item of
evidence.
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The evidence container must be marked for identification
The collector’s initials should be placed on the seal
If evidence is turned over to another person, the transfer
must be recorded.
Crime Scene Reconstruction
Stages
Data collection
§  Hypothesis formation
§  Examination, testing and analysis
§  Determination of the significance of the
evidence
§  Theory formulation
§ 
Investigators
“The wise forensic investigator will always
remember that he must bring all of his life
experiences and logic to find the truth. This means
common sense, informed intuition, and the
courage to see things as they are. Then he must
speak honestly about what it adds up to.”
—Dr. Henry Lee
Chief Emeritus for Scientific Services and the
former Commissioner of Public Safety for the state of Connecticut
The Medical Examiner and the Coroner
§  A medical examiner is a medical doctor, usually a
pathologist and is appointed by the governing body of the
area. There are 400 forensic pathologists throughout the
U.S.
§  A coroner is an elected official who usually has no special
medical training. In four states, the coroner is a medical
doctor.
Medical Examiner’s Responsibilities
§  Identify the deceased
§  Establish the time and date of death
§  Determine a medical cause of death—the injury or disease that resulted
in the person dying
§  Determine the mechanism of death—the physiological reason that the
person died
§  Classify the manner of death
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Natural
Accidental
Suicide
Homicide
Undetermined
§  Notify the next of kin
The Corpse
“The way I see it, being dead is not terribly far off
from being on a cruise ship. Most of your time is
spent lying on your back. The brain has shut
down. The flesh begins to soften. Nothing much
new happens, and nothing is expected of you.”
—Mary Roach. Stiff. W. W. Norton & Company.
2003