Transcript forensic science - Valhalla High School

FORENSIC
SCIENCE
Introduction
and
Crime Scene
Investigation
Forensic Science
•The word forensic is derived from the Latin forensis,
meaning forum, a public place where, in Roman times,
senators and others debated and held judicial proceedings.
•Forensic Science is the study and application of science to
matters of the law. (The term criminalistics is often used
interchangeably with forensics.)
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Forensic Science
Forensic scientists use crime labs to help them examine evidence. Most crime labs
will include several departments:
physical science (including chemistry, physics, and geology)
biology
ballistics
document examination
photography
toxicology and drug analysis
fingerprints
Besides using the departments listed above, forensic crime labs may also consult
specialists in the following fields:
anthropology
computer technology
voiceprint analysis
psychiatry
pathology
taphonomy
odontology
entomology
etc…
engineering
polygraphy
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What is the role of forensics?
• It is important to realize that the forensic scientist must
pull from a wide array of knowledge and specialists to
competently do his or her job.
• Forensics is more of a team effort than one would
imagine. (Forget CSI folks…….the real world is
nothing like that.)
• A death that is unexpected or is thought to have been
caused by an injury or poison is always investigated
for the purpose of determining whether or not it was a
homicide.
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Methodology
The forensic scientist must be methodical in his or
her work. He or she must first observe general
characteristics of the evidence then observe
more specific features. He or she must link
evidence to a crime and to the suspects by
identifying and comparing relevant material.
All forensic scientists use the scientific method to
conduct their investigations.
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Criminal Justice and the Law
There are a number of different kinds of law in the U.S.
criminal justice system:
1. The U.S. Constitution – the supreme body of laws
that governs our country. It overrules the
constitutions of the individual states.
2. Statutory law – this is also called written or codified
law and is the law on the books as enacted by a
governmental body or agency having the power to
make laws (such as congress). Statutory law is based
on the constitution.
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Criminal Justice and The Law
3.
4.
Common Law or Case Law – these are laws made by judges.
Precedents are set in appellate courts. The principle of
recognizing previous decisions as precedents is called stare
decisis, meaning “ to stand by the decision.” This makes for
predictability and consistency in how laws are applied.
Civil Law - Sometimes referred to as private law which deals
with relationships between individuals involving such matters
as property or contracts. It provides a formal means for
conducting non-criminal business between individuals,
businesses or agencies of government and other organizations.
Civil cases are more interested in assigning blame than
discovering intent. Civil cases usually involve a
preponderance of evidence to convict. Violations of civil law
are usually in the form of fines or transfer of prosperities.
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Criminal Justice and the Law
5. Criminal Law – sometimes referred to as
public law and deals with the regulation and
enforcement of rights. Typically deals with
offenses against an individual that are deemed
offensive to society; the state becomes the
plaintiff. In criminal cases, the prosecution
must prove guilt.
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A misdemeanor is a minor crime such as theft.
A felony is a major crime such as murder or rape.
Prosecution must prove guilt beyond a shadow
of a doubt in order to convict.
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Criminal Justice and the Law
6. Equity law - is remedial or preventative law.
This may include things like injunctions or
restraining orders. This will also include
orders of protective custody.
7. Administrative law – includes rules or laws
established by agencies such as the IRS,
Social Security Administration, or branches of
the military.
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Bill of Rights
1. Innocent until proven guilty
2. Not to be searched unreasonably
3. Not to be arrested w/out probable
cause
4. Against unreasonable seizure of
personal property
5. Against self incrimination
6. Right to fair questioning
7. Right to protection from physical
harm throughout the justice process
8. Right to an attorney
9. Right to trial by jury
10. Right to know any charges against
oneself.
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Right to cross examination.
Right to speak and present
witnesses
Right not to be tried of the same
crime
Right against cruel and unusual
punishment
Right to due process
Right to a speedy trial
Right against excessive bail and
fines
Right to be treated the same as
others regardless of race, gender,
religious preferences, country of
origin, and other personal
attributes.
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Steps in Pursuing Justice
The steps are complex and confusing because of different
jurisdictions (federal, state, local), different state rules
and procedures, the type of crime committed, and a
myriad of other factors influencing a case.
Once a crime is committed, it must first be discovered,
and a suspect may or may not be identified. Police
investigate the crime and collect information and
evidence.
After an investigation ensues, and if there is enough
evidence to establish probable cause, an arrest warrant
is issued.
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Steps in Pursuing Justice
After arrest, the suspect is booked, and fingerprinted,
photographed and informed of his/her Miranda rights.
At this time the person is also informed of any charges
being brought upon them.
Within 72 hours of arrest, the suspect is brought before a
magistrate, judge or commissioner for arraignment.
An arraignment is a preliminary procedure in which the
accused is informed of the charges and bail. The
suspect also enters a plea at this point.
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Steps in Pursuing Justice
A person who pleads guilty is taken before a court
for an evidentiary hearing; there is no jury.
Some states require a grand jury for this step. The
grand jury will decide on whether the accused
will be indicted and then a trial date is set.
Plea bargaining can occur at many points in the
judicial process. About 90 percent of cases are
plea bargained and settled without ever going to
trial.
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Federal Rules of Evidence
The rules provide a platform for evidence to be presented
in a trial. Evidence must be probative (must prove
something) and not hearsay.
Expert Witness: a person who is a specialist in a subject,
often technical who may present his or her expert
opinion without actually witnessing any occurrence
relating to the case. This is an exception to the rule
against giving an opinion in a trial, provided that the
expert is qualified by his or her expertise, training, or
special knowledge.
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Federal Rules of Evidence
The Frye standard – commonly called the general acceptance test.
The Frye standard dictates that scientific evidence is admissible
at trial only if the methodology or principle on which the
opinion is based is sufficiently established to have gained
general acceptance in the particular field to which it belongs.
This applies to new or novel scientific methodologies.
The Daubert Ruling- an updated revision of the Frye standard.
Applies only in federal courts, but states are expected to use the
decision as a guideline in setting standards. The trial judge must
assume responsibility for admissibility and validity of evidence
presented in his or her court.
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CORPUS DELICTI
• You must prove:
“Body of the Crime”
• that a crime has 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
Sex
Emotion--love, hate, anger
• Source of Evidence
• Body
• Primary and/or Secondary Crime Scene
• Suspect(s)
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Crime Scene Team
• A group of professionals investigators, each trained in a variety
of special disciplines.
• Team Members
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First Police Officer on the scene
Medics (if necessary)
Investigator(s)
Medical Examiner (if necessary)
Photographer and/or Field Evidence Technician
Lab Experts
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pathologist
DNA expert
forensic odontologist
forensic psychologist
firearm examiner
document and handwriting experts
serologist
toxicologist
forensic anthropologist
forensic entomologist
bomb and arson expert
fingerprint expert
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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 1924.
• The Scientific Crime Detection Lab was founded
in Evanston, Illinois in 1929.
• The first FBI crime lab opened in 1932.
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Edmond Locard
• French professor
• Considered the father of criminalistics
• Built the world’s first forensic laboratory in
France in 1910
• Postulate--Locard Exchange Postulate
• Whenever two objects come into contact with each other,
traces of each are exchanged.
• “Every contact leaves a trace.”
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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
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First Officer
at the Scene
• A
Assess the crime scene
• D
Detain the witness
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Arrest the perpetrator
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Protect the crime scene
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Take notes
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Eye Witness
“Perception is reality.”
As a result an eye witness may
not be the best source of
crime scene information.
A police composite may be
developed from the witness
testimony by a computer
program or forensic artist.
Faces Composite Program
by InterQuest
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Eye Witness
• Juries can be heavily influenced by eyewitness
accounts. But how accurate are they?
• Eyewitnesses can make perceptual errors for many
reasons:
• crime scene was too dark, encounter was too brief, or the
presence of a weapon may have diverted their attention
• the stress and fear involved in witnessing a crime may
sharpen some people’s focus and confuse others
• the time between the crime and questioning
• new information – viewing mug shots or being asked
leading questions
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A TRUE EYEWITNESS
Crazy Criminal
As a female shopper exited a New York
convenience store, a man grabbed her purse
and ran. The clerk called 911 immediately and
the woman was able to give them a detailed
description of the snatcher. Within minutes, the
police had apprehended him. They put him in
the car and drove back to the store. The thief
was then taken out of the car and told to stand
there for a positive ID, with that he replied,
“Yes, Officer. . That’s her. That’s the lady I
stole the purse from.”
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What is the value of Physical Evidence?
• It can prove that a crime has been committed
and set the scene for the investigation.
• It can back up witness or prove it false.
• It can link a suspect with a victim or with a
crime scene.
• It can determine the identity of people
associated with a crime.
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It can allow investigators to reconstruct a crime.
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Evidence
Characteristics
Class - common to a group of objects or persons; a group
of objects that share properties or characteristics (this
evidence considered mainly circumstantial)
Individual - can be identified with a particular person or
single source.
ABO Blood Typing
Blood DNA Typing
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Physical Evidence
1. Transient Evidence –
temporary, easily changed or lost,
usually observed by the first
officer at the scene
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Odor - putrefaction, perfume,
gasoline, urine, burning, explosives,
cigarette or cigar smoke
Temperature - of room, car hood,
coffee, water in a bathtub; cadaver
Imprints and indentations footprints; teeth marks in perishable
foods; tire marks on certain surfaces
Markings
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Physical Evidence
2. Pattern or Transfer Evidence produced by direct contact
between a person and an object or
between two objects. There are
several ways of classifying
evidence. In this class, we will
use:
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Biological
Chemical
Physical
Miscellaneous
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Biological Evidence
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Blood
Semen
Saliva
Sweat/Tears
Hair
Bone
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Tissues
Urine
Feces
Animal Material
Insects
Bacterial/Fungal
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Chemical Evidence
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Fibers
Glass
Soil
Gunpowder
Metal
Mineral
Narcotics
Drugs
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Paper
Ink
Cosmetics
Paint
Plastic
Lubricants
Fertilizer
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Physical (impression)
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Fingerprints
Footprints
Shoe prints
Handwriting
Firearms
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Printing
Number restoration
Tire marks
Tool marks
Typewriting
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Miscellaneous
• Laundry marks
• Voice analysis
• Polygraph
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Photography
Stress evaluation
Psycholinguistic analysis
Vehicle identification
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Physical Evidence
3. Conditional Evidence - produced
by a specific event or action;
important in crime scene
reconstruction and in determining the
set of circumstances within a
particular event.
• 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
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Physical Evidence
Conditional Evidence (cont.)
• Location--of injuries or wounds; of bloodstains; of the
victims vehicle; of weapons or cartridge cases; of
broken glass, etc.
• 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.
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Forensic Investigations
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Include some or all of these seven major
activities
1. Recognition - ability to distinguish important
evidence from unrelated material
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Pattern recognition
Physical property observation
Information analysis
Field-testing
2. Preservation - collection and proper preservation
of evidence
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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 know standards or controls. If all
measurements are equal, then the two samples are
considered to have come from the same source or
origin.
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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 case events
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Inductive and deductive logic
Statistical data
Pattern analysis
Results of laboratory analysis
Lee, Henry, Dr.. Famous Crimes. Southington: Strong Books, 2001.
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Just A Thought
It’s not what you know that hurts
you, its what you think you know
and it’s not so.
- Mark Twain
How does this apply to
forensic science and crime
investigations?
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