Transcript Crime Scene Evidence powerpoin

Forensic Science:
An Introduction
Forensic Science
In its broadest definition it is the
application of science to law
 Applies to the knowledge and technology
of science for the definition and
enforcement of such laws
 Definition: the application of science to
those criminal and civil laws that are
enforced by police agencies in a criminal
justice system
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Sciences involved
Chemistry
 Biology
 Physics
 Geology
 Forensic pathology
 Forensic psychology
 Forensic Odontology
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History of Forensic Science
Sir Arthur Conan Doyle: fictional character
Sherlock Holmes had a great influence on
popularizing the study of crime scenes
 Holmes was the first to apply the principles
of serology (blood typing and analysis),
fingerprinting, firearm identification and
document examination
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First book in 1887 “A Study in Scarlet”
Important People
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Mathieu Orfila (1787-1853) father of
forensic toxicology; detection of poisons
and their effects
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Alphonse Bertillon (1853-1914) scientific
system for personal identification; taking
body measurements as a means of
distinguishing people; father of criminal
identification
Important People
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Francis Galton (1822-1911) study of
fingerprints and developed method for
classifying them for filing
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Karl Landsteiner in 1901 discovered ABO
blood types
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Leone Lattes (1887-1954) devised a
procedure for determining blood group of a
dried bloodstain
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Calvin Goddard (1891-1955) comparison
microscope to identify bullets
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Albert Osborn (1858-1946) document
examination
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Walter McCrone (1916-2002) known as
the world’s preeminent microscopist;
instructor, and author
Important People
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Hans Gross (1847-1915) Austrian judge
who described the application of scientific
disciplines to the field of criminal
investigation.
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Zoology, botany, anthropology, fingerprinting
Edmond Locard (1877-1966) founder and
director of the Institute of Criminalistics at
the University of Lyons; workable crime lab
Important People
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Edmond Locard:
Locard’s Exchange Theory: the exchange of
materials between two objects that occurs
whenever two objects come into contact with
one anther
 Locard believed every criminal can be
connected to a crime by dust particles carried
from the crime scene
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Major influencers
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#1 reason for increased need of trained
scientists is the increase in drug sale and
usage in the world
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All illicit drug seizures must be sent to a
forensic lab for confirmatory chemical analysis
before the case can go to court
4 Federal Crime Labs
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FBI: largest crime lab
DEA Drug Enforcement Agency: analysis of
drugs seized in violation of federal laws for
production, sale and transportation of drugs
ATFE Bureau of Alcohol Tobacco Firearms and
Explosives: responsible for analyzing alcoholic
beverages and documents relating to tax law
enforcement and for examining weapons,
explosive devices, and related evidence
U.S. Postal Inspection Services: maintains lab
concerned w/criminal investigations relating to
the postal service
Crime Lab Services
Basic Services
 Photography
 Physical Science
 Biology/DNA
 Firearms
 Document
Examination
Optional Services
 Toxicology
 Latent Fingerprint
 Polygraphy
 Voice Analysis
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Forensic Psychiatry
Forensic Odontology
Forensic Engineering
Forensic Computer
and Digital Analysis
What Forensic Scientists Do
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Analyze physical evidence
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Determine admissibility of evidence
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Use scientific methods
Frye v US (1923) – general acceptance
Judge scientific evidence
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Daubert case (1993) – trial judge is gatekeeper
Provide expert testimony
 Furnish training
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Physical Evidence
Anything physical objects that can link a
crime to its victims or to suspects.
 Has to be collected from crime scene
 Must be relevant to the crime
 Requires the collector to understand what
the capabilities and limitations of the crime
lab are
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Physical Evidence
Crime labs do not solve crimes, only add
evidence to help police investigation link
the suspect to the crime.
 The forensic scientists must know how to
collect and preserve evidence found at the
crime scene
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Arriving at the Crime Scene
Secure and isolate the crime scene
 Determine boundaries of crime scene and
priorities for evidence collection
 Rough sketch
 Finished sketch
 Photograph
 Videotaping
 Notes
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Collecting Evidence
Conduct a systematic search for evidence;
be unabiased and thorough.
 Field technicians
 What to look for depends on the crime and
what specific locations of the crime scene
would most likely be affected
 Microscopic or massive objects
 Collect carriers of possible evidence
 Vacuum or sweeping collected
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Packaging of Evidence
Prevent any changes from occurring
(contamination, breakage, evaporation,
bending, loss)
 Process trace evidence from original
object (shirt, shoe) rather than isolating
and packaging if possible
 Package evidence separately
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Tools for Collecting Evidence
Forceps
 Evidence envelopes and pill bottles
 Swabs
 Special concerns (mold, evaporation)
 Various light sources
 Latent fingerprints
 Mobile crime labs or better yet crime
scene search vehicle
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Chain of custody
Continuity of possession; every person
who touched it must be accounted for
 Standards for collecting, labeling, and
submitting evidence forms are necessary
for court
 Labels include collectors initials, location
of evidence, date of collection.
Identification numbers must also be used
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Submission of Evidence
Standard/reference samples
 Substance controls
 Evidence submission form will detail the
evidence collect and particular type of
examination/analysis requested.
 Lab tech not bound by requests
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Common Types of Evidence
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Common Types of
Evidence
Blood, semen, and saliva
Documents
Drugs
Fibers
Fingerprints
Firearms and ammunition
Glass
Hair
Impressions
Organs and physiological
fluids
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Paint
Petroleum products
Plastic bags
Plastic, rubber, and other
polymers
Powder residues
Serial numbers
Soil and minerals
Tool marks
Vehicle lights
Wood and other
vegetative matter
Examination of Physical Evidence
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Identification
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Determining the identity of a substance with a near
absolute certainty while ruling out other substances
Comparison
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Comparing the evidence to one or more selected
references and drawing a conclusion about its origins.
Individual characteristics –properties of evidence that
can be attributed to a common source with extremely
high certainty. (eg. fingerprints, DNA, bullets)
Class characteristics – properties of evidence that
can be associated with a group and never with a
single source. ( eg. Blood type, tire marks)
Significance of Physical Evidence
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Assessing the values of evidence
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Class characteristics of evidence is valuable in
corroborating events.
Multiple class evidence can lead to a high level of
certainty of origin
Cautions and limitations of evidence
A person can be exonerated or excluded from
suspicion if evidence collected from the crime
scene is different from the reference samples
collected from the person.
Forensic Databases
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One-on-one comparison requires a suspect
Computerized databases help link evidence to
people
Fingerprint databases – IAFIS
DNA database – CoDIS
Ballistics database – IBIS
Automative Paint database – PDQ
Shoeprint database - SICaR