Transcript Forensic Science - SCHOOLinSITES - The Official Site

Unit 1
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What is Forensic Science?
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Forensic Science – application of science to
law
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Who are some important people that have
contributed to the field of forensic science?
What have these people contributed?
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Fictional character developed by author Sir
Arthur Conan Doyle
First to apply serology, fingerprinting, firearm
identification, and questioned document
examination
All of this – from fiction – before accepted by
real-life criminal investigations.
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Father of Toxicology
Lafarge Trial (Marie) – arsenic
Book: Traite des poisons or Toxicologie
generale – first scientific study of the
detection and pathological effects of poisons
– established toxicology as a distinct field of
forensic science.
The father of criminal
identification
 Developed
anthropometry – using
body length
measurements as
unique properties –
took 243 separate
measurements
 Method was coined
“Bertillonage”
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Fingerprinting
 Developed methodology for identification using
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the friction ridges on fingers
Basics still used today
His work has been enhanced by Sir Edward Henry
– the father of modern fingerprinting
Henry developed a filing method for storing
fingerprint patterns/records prior to computer
storage capabilities
Wrote the book Fingerprints
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Blood testing – used technique developed by
Dr. Karl Landsteiner
Bloodstains – developed method to
determine blood type from dried blood
Discovered that blood typing could be used
as a means of identification
Father of Firearm Identification
Individualization of
weapons
 Firing pin marks on
shell casings
 Refined the technique
of bullet comparison
with the gun from
which it was fired.
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Handwriting expert –
established the
fundamental principles
of document
examination.
 Wrote Questioned
Documents
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First real life “scientific detective” – described
the application of scientific disciplines to the
field of criminal investigation.
Wrote first book on criminal investigation
Austrian lawyer
Coined the term “Criminalistics”
Wrote about: forensic medicine toxicology,
serology, ballistics, and anthropometry
Suggested using: mineralogist, ecologist, and
botanists
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Reorganized the
Bureau of
Investigations in 1924
 Included fingerprint
cards
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1932 now FBI
 Organized a national
laboratory that aimed to
offer forensic services of
all law enforcement
agencies
Father of Forensics
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Locard’s Exchange Principle
– whenever two objects
come in contact, material
will be exchanged between
them
Every criminal can be tied to
crime by dust particles
carried from the scene
 Example: counterfeit coins –
metal found in that matched
those of the coins found on
three suspects clothes –
confronted with evidence –
they confessed
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How are crime laboratories organized in the
United States?
What units are present in most crime labs?
What is the responsibility of the units in each
crime lab?
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5 main federal labs
 Department of Justice (DOJ) labs at the Federal
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Bureau of Investigation (FBI)
United States Secret Service (USSS)
Department of Treasury labs at the Drug
Enforcement Administration (DEA)
Bureau of Alcohol, Tobacco, and Firearms (ATF)
Postal Inspection Services (PIS) at the U.S. Postal
Service (USPS)
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Main lab in US is run by FBI and serves as a
central repository for forensic info
Example
 Integrated Fingerprinting Identification System
(IAFIS)
 Combined DNA Indexing System (CODIS)
 Comparison standards for paint samples, tire
patterns, bullets, explosives, and fibers, etc
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Initially established to combat counterfeiting
issues
Protected Grover Cleveland on part-time
basis
Officially assigned to protect the president
after the assassination of William McKinley
Maintains questioned documents lab
Analyze ink and paper to determine
authenticity
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Analyze drugs for major components,
determine side products, solvents, impurities,
and starting ingredients
Determine geographical origin of illegal drug
manufacturer
Allow monitoring of patterns of drug
trafficking and development of illegal
substances
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Analyze physical evidence related to arson,
explosives, firearms, tobacco, and alcohol
In conjunction with FBI developed National
Integrated Ballistics Information Network
(NIBIN)
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Mail crimes i.e. identify theft, mail fraud,
letter bombs, child pornography
Can analyze envelope for location & criminal
id
Sometimes DNA can be isolated from saliva
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Chemistry
 Largest unit because most evidence is drug-
related and 6th amendment guarantees right to
speedy trial
 gas chromatograph-mass spectrometer for drug
analysis
 Analyze trace evidence, explosives, metals,
paints, minerals
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Physics
 Crime scene reconstruction (car accident)
 Reconstruct shooting
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Biosciences
 Analyze biological material for DNA i.e. blood,
semen, saliva, skin, hair, etc
 Identify biological samples
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Toxicology
 Analyze body fluids for presence of drugs or
poisons
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Firearms
 Comparison microscopy
▪ Match markings left on cartridge cases by firing pin,
breechblock, extractor, or ejector
▪ Match test fired bullet
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Fingerprints
 Uncover latent prints by dusting, chemical,
ultraviolet, and alternative light techniques
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Photography
 Record the crime scene
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Questioned Documents
 Forged, altered, counterfeit documents
 Analyze ink, handwriting, printing, erasures
obliterations, and charred documents
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Evidence Collection
 Trained evidence collection technicians travel to
crime scene
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Evidence Submission and Holding
 Maintain chain of custody, secure evidence
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What is the role of the forensic scientist?
What is the role of the crime scene
investigator?
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Main job – analyze evidence
Train law enforcement (CSI) to identify,
collect, and preserve evidence
Expert witness
Use physical evidence to connect the crime
scene, the victim, and the criminal
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Recognize, collect, preserve evidence
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What are different careers in Forensic
Science?
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Medical examiner
 Physician authorized by state to investigate,
unexpected, violent, suspicious, or unnatural
deaths
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Pathologist
 Physician trained in determining cause of death;
autopsy
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Toxicologist
 Detects presence of poisons or drugs in body
fluids, tissues, and organs
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Odontologist
 Forensic dentists
 Use dental records for id especially in burn victims
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Forensic Psychiatrist
 Apply psychiatry to law
 develop profile and determine competency to
stand trial
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Forensic Engineer
 Apply engineering principle to law
 May determine structural failure such as bridge or
building collapse
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Forensic Anthropoloist
 Performs specialized examination of human
skeletal remains or badly decomposed bodies for
id purposes
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Forensic Entomologist
 Apply study of insects to law
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What is evidence?
What are the types of evidence?
What is the difference between individual and
class evidence?
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Something that tends to establish or disprove
a fact
 Examples
▪ Documents
▪ Testimony
▪ Other objects
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Evidence
 Testimonial
▪ Expert
▪ Eyewitness
 Physical
▪ Individual
▪ Class
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Person who is a specialist in a subject
Only witness who can give their opinion
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Direct witness to an event
Reliability
 Scene may have been too dark
 Encounter may have been too brief
 Presence of a weapon may have diverted the
attention of the witness
 Memory problems
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Individualized to a single, specific source
No doubt as to what the source is
 Fingerprints
 DNA
 Handwriting
 Voiceprints
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Always involves a comparison – an exemplar
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Consistent with a particular source
The more class evidence that fit the criminal –
the better
 Hair
 Fibers
 Soil
 Glass fragments
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Much evidence is circumstantial
Implies a fact or event without actually
proving it
Example
 A blond hair is found in the hand of a murder
victim with black hair
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The more circumstantial evidence the greater
the probative value
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How can the probative value of class
(identified) evidence be increased?
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Class evidence is used to narrow a suspect
pool
The more class evidence found, the stronger
the case against an individual
Scenario
 A young person was seen leaving a high
school parking lot after having been near a
car with a broken window; the car’s CD player
was missing. The suspect was identified as
having light brown hair and wearing a white
shirt, blue jeans, and dark-colored athletic
shoes. In a school of 1600 students, how
common are these characteristics?
*Note: The students do not wear uniforms.
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Suspect:
 White t-shirt
 Blue jeans
 Light brown hair
 Dark colored athletic shoes
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Population size = 1600
Sample is a typical classroom
 Sample size = 33 students
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In the sample, 7 students are wearing white tshirts, so we need to find the percentage of
students in the class wearing white shirts.
 7 wearing a white shirt divided by 33 students in
class = 0.21 or 21 %
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So, how many students is 21% of the whole
population?
 0.21 x 1600 = 336 students
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Importance: Our suspect pool has just been
narrowed from 1600 students to 336
students.
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How many students would be wearing blue
jeans? In your class, you count 12 wearing
blue jeans.
 12 wearing blue jeans divided by 33 students in
class = 0.36, or 36%
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How many students in the school would be
expected to be wearing blue jeans?
 0.36 x 1600 = 576 students
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Next, determine how many students would
be likely to have light brown hair. In your
class, you count 5 students with light brown
hair.
 5 with light brown hair divided by 33 students =
0.15 or 15%
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How many students in school would be likely
to have light brown hair?
 0.15 x 1600 = 240 students
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In your class, 4 students are wearing darkcolored athletic shoes.
 4 with dark-colored athletic shoes divided by 33
students = 0.12 or 12%
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How many students in school would be likely
to be wearing dark-colored athletic shoes?
 0.12 x 1600 = 190 students
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We have narrowed the pool four times, but
the real power of this method is finding the
probability of a person with all of these
characteristics.
In order to do this, multiply the probability of
each event together and then by the
population size.
 0.21 x 0.36 x 0.15 x 0.12 x 1600 = 2
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Grand Finale
 We have narrowed a pool of 1600 suspects down
to two because we had four pieces of class
evidence to consider.
 Therefore, the probative value continues to grow
by considering class evidence.
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A teacher’s computer is stolen from C116.
The culprit was wearing a purple shirt,
glasses, shoes with red in them. Use the class
as a sample. In a school of 1600 students,
how common are these combinations of
characteristics.