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Forensic ScienceUnit 1
Essential Question
What is Forensic Science?
Intro. to Forensic Science
Forensic Science – application of science to law
Essential Question
Who are some important people that have contributed to the field of forensic science?
What have these people contributed?
Sherlock Holmes
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.
Mathieu Orfila – 1813
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.
Alphonse Bertillon - 1879 The father of
criminal identification
Developed anthropometry – using body length measurements as unique properties – took 243 separate measurements
Method was coined “Bertillonage”
Francis Galton
Fingerprinting Developed methodology for
identification using 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
Leone Lattes - 1915
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
Calvin Goddard – 1920s
Individualization of weapons
Firing pin marks on shell casings
Refined the technique of bullet comparison with the gun from which it was fired.
Father of Firearm Identification
Albert S. Osborn
Handwriting expert – established the fundamental principles of document examination.
Wrote Questioned Documents
Hans Gross
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
J. Edgar Hoover
Reorganized the Bureau of Investigations in 1924 Included fingerprint
cards 1932 now FBI
Organized a national laboratory that aimed to offer forensic services of all law enforcement agencies
Edmond Locard
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
Father of Forensics
Essential question
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?
Organization
5 main federal labs Department of Justice (DOJ) labs at the
Federal 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)
Organization Cont.
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
USSS
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
DOJ lab at DEA
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
ATF
Analyze physical evidence related to arson, explosives, firearms, tobacco, and alcohol
In conjunction with FBI developed National Integrated Ballistics Information Network (NIBIN)
PIS @ USPS
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
Units
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
Units (Cont.)
Physics Crime scene reconstruction (car accident) Reconstruct shooting
Biosciences Analyze biological material for DNA i.e.
blood, semen, saliva, skin, hair, etc Identify biological samples
Toxicology Analyze body fluids for presence of drugs
or poisons
Units (Cont.)
Firearms Comparison microscopy▪ Match markings left on cartridge cases by firing
pin, breechblock, extractor, or ejector▪ Match test fired bullet
Fingerprints Uncover latent prints by dusting, chemical,
ultraviolet, and alternative light techniques
Photography Record the crime scene
Units (Cont)
Questioned Documents Forged, altered, counterfeit documents Analyze ink, handwriting, printing,
erasures obliterations, and charred documents
Evidence Collection Trained evidence collection technicians
travel to crime scene Evidence Submission and Holding
Maintain chain of custody, secure evidence
Essential Question
What is the role of the forensic scientist?
What is the role of the crime scene investigator?
Forensic Scientists
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
Crime Scene Investigator
Recognize, collect, preserve evidence
Essential Question
What are different careers in Forensic Science?
Careers
Medical examiner Physician authorized by state to
investigate, unexpected, violent, suspicious, or unnatural deaths
Pathologist Physician trained in determining cause
of death; autopsy Toxicologist
Detects presence of poisons or drugs in body fluids, tissues, and organs
Careers (Cont.)
Odontologist Forensic dentists Use dental records for id especially in
burn victims Forensic Psychiatrist
Apply psychiatry to law develop profile and determine
competency to stand trial
Careers (Cont.)
Forensic Engineer Apply engineering principle to law May determine structural failure such as
bridge or building collapse Forensic Anthropoloist
Performs specialized examination of human skeletal remains or badly decomposed bodies for id purposes
Forensic Entomologist Apply study of insects to law
Essential Question
What is evidence? What are the types of evidence? What is the difference between
individual and class evidence?
Evidence
Something that tends to establish or disprove a fact Examples▪ Documents▪ Testimony▪ Other objects
Types of Evidence
Evidence Testimonial ▪ Expert▪ Eyewitness
Physical▪ Individual▪ Class
Expert Witness
Person who is a specialist in a subject
Only witness who can give their opinion
Eyewitness
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
Individual
Individualized to a single, specific source
No doubt as to what the source is Fingerprints DNA Handwriting Voiceprints
Always involves a comparison – an exemplar
Class Evidence
Consistent with a particular source The more class evidence that fit the
criminal – the better Hair Fibers Soil Glass fragments
Circumstantial Evidence
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
The more circumstantial evidence the greater the probative value
Essential Question
How can the probative value of class (identified) evidence be increased?
Class Evidence
Class evidence is used to narrow a suspect pool
The more class evidence found, the stronger the case against an individual
Probability and Class EvidenceScenario 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.
Probability and Class Evidence
Suspect: White t-shirt Blue jeans Light brown hair Dark colored athletic shoes
Population size = 1600 Sample is a typical classroom
Sample size = 33 students
Probability and Class Evidence In the sample, 7 students are wearing
white t-shirts, 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 % So, how many students is 21% of the
whole population? 0.21 x 1600 = 336 students
Importance: Our suspect pool has just been narrowed from 1600 students to 336 students.
Probability and Class Evidence
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% How many students in the school
would be expected to be wearing blue jeans? 0.36 x 1600 = 576 students
Probability and Class Evidence
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% How many students in school would
be likely to have light brown hair? 0.15 x 1600 = 240 students
Probability and Class Evidence
In your class, 4 students are wearing dark-colored athletic shoes. 4 with dark-colored athletic shoes
divided by 33 students = 0.12 or 12% How many students in school would
be likely to be wearing dark-colored athletic shoes? 0.12 x 1600 = 190 students
Probability and Class Evidence
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
Probability and Class Evidence
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.
Solve the following:
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.