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.