Transcript Forensic Science Introduction

Forensic Science
INTRODUCTION
What is forensic science?
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Forensic science is the application of
science to criminal and civil laws.
This course emphasizes the
application of science to those
criminal and civil laws that are
enforced by police agencies in a
criminal justice system.
Forensic science owes its origins to
many scientists who developed the
principles and techniques needed to
identify or compare physical
evidence.
History of Forensic Science
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Mathieu Orfila (1813) —the father of forensic
toxicology; published a treatise.
Alphonse Bertillion—devised the first scientific
system of personal identification in 1879.
Francis Galton—conducted the first definitive
study of fingerprints and their classification.
Leone Lattes—developed a procedure to
determine blood type from dried bloodstains.
Calvin Goddard—used a comparison
microscope to determine if a particular gun
fired a bullet.
Albert Osborn—developed the fundamental
principles of document examination.
History of Forensic Science
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Walter McCrone—utilized microscopy and other analytical
methodologies to examine evidence.
Hans Gross —wrote the first treatise describing the application of
scientific principles to the field of criminal investigation. The “father
of criminal investigation.”
Edmond Locard—incorporated Gross’ principles within a workable
crime laboratory.
Locard’s Exchange Principle—states that when a criminal comes in
contact with an object or person, a cross-transfer of evidence
occurs. “Every contact leaves a trace.”
Locard’s Exchange Principle
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The Locard Exchange Principle states that
whenever two objects come into contact, a mutual
exchange of matter will take place between them.
VICTIM
SUSPECT
PHYSICAL EVIDENCE
OBJECT
CRIME SCENE
Corpus Delicti
“Body of the Crime”
A crime must have been proven to be committed before
someone is convicted of having committing the crime.
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You must prove
 That a crime occurred
 That the person charged with the crime was responsible for the crime
Sources of physical evidence
 Body
 Suspect
 Primary and secondary crime scenes
Facets of Guilt
The common summation of the three aspects of a crime
that must be determined before a conviction
 Means – the ability to have committed a crime
 Motive – the reason for committing the crime (This does
not have to be proven in the court of law but it is what
everyone wants to know!)
 Opportunity – time or availability to have committed the
crime
The court cannot convict on these three things along …
the prosecution must present evidence!
Where is evidence analyzed?
How long does it take to analyze
evidence?
What is the CSI Effect?
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The CSI effect, also known as
the CSI syndrome and the CSI infection, is
any of several ways in which the
exaggerated portrayal of forensic science
on crime television shows such as CSI:
Crime Scene Investigation influences public
perception.
CSI Effect
CSI Disney
The Crime Lab
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The development of crime laboratories in
the United States has been characterized
by rapid growth accompanied by a lack of
national and regional planning and
coordination.
At present, approximately 400 public crime
laboratories operate at various levels of
government—federal, state, county, and
municipal.
FBI Crime Lab
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1932 – FBI Crime Lab founded.
The Crime Lab
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The ever increasing number of crime laboratories is partly the
result of the following:
 Supreme Court decisions in the 1960s responsible for police
placing greater emphasis on scientifically evaluated evidence.
 Crime laboratories inundated with drug specimens due to
accelerated drug abuse. (All illicit drug seizures must be sent
to forensic laboratory for confirmatory chemical analysis before
the case can be adjudicated.
 The advent of DNA profiling.
 Increasing crime rates coupled with fewer confessions
because people know their rights!
Major Federal Crime Labs
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Federal Bureau of
Investigation (FBI)
Drug Enforcement
Administration (DEA)
Bureau of Alcohol,
Tobacco, Firearms, and
Explosives
US Postal Inspection
Service
Basic Services in Full Service Labs
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The technical support provided by crime laboratories
can be assigned to five basic services.
 Physical Science Unit incorporates the principles of
chemistry, physics, and geology to identify and
compare physical evidence. (drugs, soil, glass,
paint)
 Biology Unit applies the knowledge of biological
sciences in order to investigate blood samples,
body fluids, hair samples.
 Firearms Unit investigates discharged bullets,
cartridge cases, shotgun shells, and ammunition.
Basic Services
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Document Unit provides
the skills needed for
handwriting analysis and
other questioneddocument issues.
Photography Unit applies
specialized photographic
techniques for recording
and examining physical
evidence.
Optional Services
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Optional Services by Full-Service Labs
 Toxicology Unit examines body fluids and organs for
the presence of drugs and poisons.
 Latent Fingerprint Unit processes and examines
evidence for latent fingerprints.
 Polygraph Unit conducts polygraph or lie detector
tests.
 Voiceprint Analysis Unit attempts to tie a recorded
voice to a particular suspect.
 Evidence-Collection Unit dispatches specially trained
personnel to the crime scene to collect and preserve
physical evidence.
The forensic scientist
Skills of a Forensic Scientist
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A forensic scientist must be skilled in applying the
principles and techniques of the physical and natural
sciences to the analysis of the many types of evidence
that may be recovered during a criminal investigation.
A forensic scientist may also provide expert court
testimony.
An expert witness is an individual whom the court
determines possesses knowledge relevant to the trial
that is not expected of the average person.
(An ordinary witness must give testimony on events or
observations that arise from personal knowledge.
Testimony must be factual and cannot give opinions.
Skills of a Forensic Scientist
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The expert witness is called on to evaluate evidence
based on specialized training and experience that the
court lacks the expertise to do.
The expert will then express an opinion as to the
significance of the findings.
Forensic scientists also participate in training law
enforcement personnel in the proper recognition,
collection, and preservation of physical evidence.
Analysis of Physical Evidence
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Forensic scientists must be aware of the
demands and constraints imposed by the
judicial system.
The procedures and techniques used in a
laboratory must not only rest on firm
scientific foundation but also must satisfy
the criteria of admissibility that have been
established by the courts.
The Frye Standard
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The Frye v. United States decision
set guidelines for determining the
admissibility of scientific evidence
into the courtroom.
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To meet the Frye standard, the
evidence in question must be
“generally accepted” by the
scientific community.
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Frye Not Absolute
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However, in the 1993 case of Daubert v. Merrell
Dow Pharmaceutical, Inc., the U.S. Supreme
Court asserted that the Frye standard is not an
absolute prerequisite to the admissibility of
scientific evidence.
Trial judges were said to be ultimately
responsible as “gatekeepers” for the
admissibility and validity of scientific evidence
presented in their courts, as well as all expert
testimony.
The Daubert Criteria
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In Daubert, the Supreme Court offered some guidelines as to how
a judge can gauge scientific evidence:
1) Whether the scientific technique or theory can be (and has been)
tested.
2) Whether the technique or theory has been subject to peer review
and publication.
3) The technique’s potential rate of error.
4) Existence and maintenance of standards controlling the
technique’s operation.
5) Whether the scientific theory or method has attracted
widespread acceptance within a relevant scientific community.
Hmmmm …
Special Forensic Science Services
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A number of special forensic science services
are available to the law enforcement community
to augment the services of the crime laboratory.
These services include forensic pathology,
forensic anthropology, forensic entomology,
forensic psychiatry, forensic odontology,
computer science, forensic engineering, among
many others.
Switching gears …
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Anytime there is a death associated with
accidents, violence, injuries, or unexplained
causes, we look to the body to provide
clues as to what happened and how it
happened.
“This is the place where death rejoices to
help those who live.”
Special Forensic Science Services
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Forensic Pathology involves the
investigation of unnatural,
unexplained, or violent deaths.
 Forensic pathologists in their
role as medical examiners or
coroners are charged with
determining cause of death.
 The forensic pathologist may
conduct an autopsy which is the
medical dissection and
examination of a body in order
to determine the cause of death.
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Medical Examiner vs. Coroner
There are two systems of death investigation in the US
today.
 A medical examiner is a medical doctor, usually a
pathologist, who is appointed by the governing body of
the area.
 A coroner is an elected official who usually has no
special medical training but is legally responsible for
overseeing death investigations.
**Any responsibilities the coroner cannot complete, will be
contracted out to a forensic pathologist.
Medical Examiner’s Responsibilities
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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.
 Natural
 Accidental
 Suicide
 Homicide
 Undetermined
Notify the next of kin.
Sign the death certificate.
So …
One can die from a massive hemorrhage
(mechanism of death) due to a gunshot
wound through the head (cause of death)
as a result of being shot (homicide),
shooting oneself (suicide), dropping a gun
and discharging it (accident), or not being
able to tell (undetermined). All of which
are manners of death.
Something to think about …
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In our legal system, injuries always take precedence over disease
for determining the cause of death.
Ex) A person could have severe heart disease long before they are
mildly assaulted. In a normal person, the assault might have
caused little more than a bruise but in this case, it could have
triggered a heart attack that led to the person’s death. The cause of
death in this case would have been determined to be from the blunt
force trauma (assault), with the heart disease as a contributing
cause. The manner of death here would be homicide.
Similarly, if a person is shot and recovers but dies 20 years later
from pneumonia, it might be determined that the death was cuased
by the older gunshot injury with pneumonia as a contributing factor.
This would mean the death is classified as a homicide.
Now you tell me …
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A motorcycle accident leaves a man with a fractured tibia that is set in the
hospital and the person recovers. Over a number of years, however, an
infection of the broken bone sets in that ultimately develops into a cancer in
the open space left in the bone by the original accident. The cancer goes
undetected for years until it metastasizes elsewhere in the body. The
cancer eventually kills the man more than twenty years after the original
motor cycle accident.
What would YOU determine to the be manner, cause, and mechanism of
death?
Answer:
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Manner: accidental
Cause: cancer
Mechanism: metastatic squamous cell carcinoma with contributing infection
Let’s talk about dead bodies …
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
Stiff: The Curious Lives of Human Cadavers
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The book covers 12 topics:
Practicing cosmetic surgery on cadaver heads
Body snatching and the early years of human dissection
The nature of decomposition
Cadavers for use as crash test dummies
Using cadavers to analyze a crash site
Army tests on cadavers
Crucifixion experiments
Beating heart cadavers, the soul, and being buried alive
Decapitation and human head transplant
Cannibalism in the name of medicine
New alternatives to burial and cremation
The author's views on her own remains
After death …
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After a human body expires there are several stages of death.
 Rigor mortis results in the shortening of muscle tissue and the
stiffening of body parts in the position at death (occurs within the
first 8 hours and usually disappears within 36 hours though can
linger up to 72 hrs).
 Livor mortis results in the settling of blood in areas of the body
closest to the ground (begins immediately on death and
continues up to 12 hours). After 12 hours the lividity is FIXED.
 Algor mortis results in the loss of heat by a body (a general rule,
beginning about an hour after death, the body loses heat by 1 to
1-1/2 degrees Fahrenheit per hour until the body reaches the
environmental temperature).
The Body
Rigor Mortis
Temperature of the
Body
Stiffness of the Body
Time since death
WARM
NOT STIFF
Less than 3 hours
WARM
STIFF
Between 3 – 8 hours
COLD
STIFF
Between 8 – 36 hours
COLD
NOT STIFF
More than 36 hours
Rigor Mortis
Livor Mortis
Livor Mortis
The Body
Algor mortis
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The cooling of the body that occurs after
death, assuming the ambient temperature
is lower than the body temperature.
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Generally the cooling rate is about 1.5°F per
hour. (Normal body temperature is 98.6°F.)
Autopsy
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An autopsy is a postmortem examination of a body in order to
answer the following questions:
 Who are you?
 When did you become ill or hurt and when did you die?
 Where did you get hurt and where did you die?
 Did you die as a result of an accident, violence, natural causes
or some combination of these reasons?
 If violence was completely or partially responsible for your
death, was it from suicide, accident, homicide, or other
reasons?
 If someone killed you, who did it?
Autopsy
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Y incision
Examination and
dissection of all internal
organs including brain
Hands
Smells
Eyes
Confessions of a Medical
Examiner
Forensic Odontology
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The application of dentistry to
human identification problems.
Forensic odontologists are
dentists who specialize in the
forensic aspect of their field.
They are concerned with the ID
of persons based upon their
dentition, usually in cases of
otherwise unrecognizable
bodies or in mass disasters.
They also analyze and
compare bite mark evidence.
Forensic Anthropology
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Personal identification based
on bodily remains (particularly
skeletal)
Practitioners are
anthropologists who are
interested in forensic science.
Other areas of forensic
anthropology include
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Maintaining databases on bodily
structures as functions of race,
sex, age, stature, etc.
Facial reconstruction
Forensic Toxicology
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The determination of
toxic substances in
human tissues and
organs.
Much of the work
concerns the role toxic
agents may have
played in causing or
contributing to the
death of a person.
Trace Evidence Analysis
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Includes all the areas of
trace and transfer
evidence, such as
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Soil and glass
Hair and fibers
Blood
Physiological fluids
Arson accelerant and
explosive residues
Drug identification
Different patterns and
imprints
Questioned Document Examination
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The comparison and
interpretation of
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Handwriting
Mechanically produced
material (typing, printing)
Photocopied material
The analysis of paper,
inks, and other materials
to produce documents.
Firearm and Toolmark Examination
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Firearm identification
Comparison of markings
on bullets, cartridge cases,
and shell cases.
Determining if a bullet has
been fired from a
particular weapon.
Toolmark examinations
are concerned with the
association of a particular
impression with a
particular tool.
Fingerprint Examinations
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Classification of
fingerprints
Maintaining fingerprint
databases
Development and
lifting of latent prints
Comparisons of
known and unknown
fingerprints to
determine a match
Forensic Entomology
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Insect activity is used to
estimate the time of death.
Specific insects present in
the body and how long a
body has been left
exposed can be
determined by examining
the stage of development
of fly larvae.
What are the goals of a forensic
scientist?
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The general goals of a forensic scientist are
Recognition of physical evidence
 Identification of physical evidence
 Individualization of physical evidence
 Reconstruction of the crime
(R.I.I.R.)
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Recognition
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Although it may seem obvious it is important to be
able to recognize what is and is not physical
evidence.
Almost anything can be physical evidence and it
is very dependent on the type of crime committed.
With practice and experience evidence
recognition becomes easier.
Beware … submitting too much evidence is just
as bad as submitting too little!
Identification
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Identification of physical evidence may be regarded as a
classification scheme.
Evidence is assigned into categories containing like items.
Initial categories are broad and then narrowed down as more
information is obtained
Example
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Blue substance
Blue paint
Blue car paint
Blue car paint from Ford Manufacturing Company
Blue car paint from Ford produced 1998-2000
Blue car paint from Ford produced 1998-2000, used on Mustang
and Explorer.
Class Evidence
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Class evidence is evidence that can be
associated with a particular group.
Class characteristics are the properties that all the
members of a certain group of objects or
substances have in common.
The “paint” is condsidered CLASS EVIDENCE.
Examples of Class Evidence
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Single layered paint
Soil
Glass fragments too small to fit back
together
Hairs
fibers
The Value of Class Evidence
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Many lawyers try to discredit class evidence because it
cannot be limited to just one possible source, however
class evidence DOES HAVE VALUE.
Look around the room, most have different clothes on.
If I were to pick a fiber from one person’s clothes in this
room, that fiber could possibly pick out the single source
or at least narrow the field.
Some class evidence holds little forensic value, such as
fiber from jeans or white cotton shirts … they are too
common!!
Individualization
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Individualization is unique to forensic science.
It refers to the idea that a particular sample is
unique, even among members of the same
class.
It may also refer to the demonstration that a
questioned piece of physical evidence and a
similar known sample have a common origin.
More than CLASS
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In addition to class characteristics, objects and materials
possess individual characteristics that can be used to
distinguish members of the same class.
The nature of these individual characteristics varies
from one type of evidence to another, but forensic
scientists try to take advantage of them in effort to
individualize a piece of physical evidence by some type
of comparison process.
Only a few types of physical evidence (primarily physical
pattern evidence) can be truly individualized.
Evidence that contains Individualizing
Characteristics
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Fingerprints
Handwriting
Bullets
Toolmarks
Shoeprints
Tire prints
Glass fragments that can be matched.
Problems with Words
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Identification is sometimes used to mean personal
identification
Fingerprints for example, can be used to “identify”
an individual
The terminology is unfortunate, since this process
is really “individualization.”
Likewise, dental evidence and dental records are
used in “identifying” dead bodies … when they are
really individualizing.
The GOAL …
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Ultimate goal would be to move all class evidence
to individualistic which is not very likely
Hair is trying to make the move … something like
paint probably never will.
For human evidence to be individualistic, the odds
of two people matching the same piece of
evidence must be 1 in about 7.5 billion, which is
the population of the earth.
Is DNA individualistic?
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Because of identical
twins, DNA is not
considered
individualistic!!
Identical twins do have
different fingerprints!
Reconstruction
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Reconstruction refers to the process of putting
the “pieces” of a case or situation together.
The objective is to reach an understanding of a
sequence of past events based on the record of
physical evidence.
Identification and individualization of physical
evidence plays a crucial role in providing data
for reconstructions.