Transcript Forencic Science Introduction Part II

Forensic Sciences: Another Introduction
Science and Law
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Forensic Science in its broadest
definition is the
application of
science to law
As our society
grows more
complex, it has
become more
dependent on laws
to regulate the
activities of its
members.
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Forensic Science
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1-Offers the knowledge and technology of
science for the definition and enforcement
of laws.
2-It cannot offer final and authoritative
solutions, however, Forensic Science does
play an important and unique roll in the
criminal justice system.
3-It uses the scientist's ability to supply
accurate and objective information that
reflects the events of a crime
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The major areas
reviewed
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The application of medicine and
medical science to legal
problems.
Practitioners of forensic
medicine are doctors of
medicine with special
certification in pathology &
forensic pathology.
Most of them are Medical
Examiners.
They are concerned with
determining cause and
circumstances in cases of
questioned death.
They also can be involved in
matters of insurance claims, &
sometimes cases of malpractice
Forensic
Medicine
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Commonly called Forensic
Dentistry
The application of dentistry to
human identification problems.
Forensic odontolgists are
dentists who specialize in the
forensic aspect of their field.
They are concerned with the
identification 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
Odontology
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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
 Maintaining data bases on
bodily structures as
functions of race, sex, age,
stature, and so forth.
 Facial reconstruction
 Interpretation of footprint or
shoe-print evidence
Forensic
Anthropology
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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.
Forensic
Toxicology
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Includes all areas of trace
and transfer evidence:
 soil and glass
 hair and fibers
 blood
 physiological fluids
 arson accelerant and
explosive residues
 drug identification
 patterns and imprints
Trace Evidence
Analysis
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Questioned
The comparison and
interpretation of ...
Documents
 handwriting
Examination
 mechanically produced
material (typing,
printing)
 photocopied material
The analysis of paper, inks,
and other materials used to
produce documents
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Firearm identification
Firearm &
Comparison of markings
Toolmark
on bullets, cartridge cases, Examination
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.
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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
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The work of a Forensic
Scientist
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The Goals of a Forensic Scientist
 Recognition
of physical evidence
 Identification of physical evidence
 Individualization of physical
evidence
 Evaluation of physical evidence
 Reconstruction of the crime
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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
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Almost anything can be physical evidence
and it is very dependant 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
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Identification
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Identification of physical evidence may be regarded
as a classification scheme
Evidence is assigned into categories with like items.
Initial categories are broad and then narrowed down
as more information is obtained
Example
 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
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Class Evidence
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To identify an object in Forensic Science is
really to separate it by class
Class characteristics are the properties that all
the members of a certain group of objects or
substances have in common.
The previous “paint” example was a refined
class evidence identification
The “paint” was identified by comparing its
class characteristics with those of known
standards or previously established criteria.
The “paint” is considered CLASS
EVIDENCE
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Class Evidence Examples
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Single layered paint
Soil
Glass fragments too small to fit back
together
Hairs
Fibers
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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 room, most have different clothes on. If
I were to pick a fiber from one persons 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
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Individualization
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Individualization is unique to Forensic
Science
It refers to the demonstration 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.
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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 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
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Evidence that Contains
Individualizing Characteristics
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Fingerprints
Handwriting
Bullets
Toolmarks
Shoeprints
Tire prints
Glass fragments that can be matched
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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
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The GOAL...
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Ultimate goal would be to move all class
evidence to individualistic, 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.
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Is DNA Individualistic??
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Up to the late 1990’s, the smallest odds were 1
in 100 million. This narrowed it to 1 in 50
people on the earth, but it still was not
individualistic.
More recently with new DNA techniques, the
new odds are proving to be “individualistic”
However we still have the problem of identical
twins having the same DNA (but they do
have different fingerprints!)
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Reconstruction
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
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