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Unit 1. Forensic Science. 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?

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Unit 1

Unit 1

Forensic Science

Essential question
Essential Question

  • What is Forensic Science?

Intro to forensic science
Intro. to Forensic Science

  • Forensic Science – application of science to law

Essential question1
Essential Question

  • Who are some important people that have contributed to the field of forensic science?

  • What have these people contributed?

Sherlock holmes
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
Mathieu Orfila – 1813

  • Father of Toxicology

  • Lafarge Trial (Marie) – arsenic

  • Book: Traite des poisons or Toxicologiegenerale – first scientific study of the detection and pathological effects of poisons – established toxicology as a distinct field of forensic science.

Alphonse bertillon 1879
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
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
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
Calvin Goddard – 1920s

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.

Albert s osborn
Albert S. Osborn

  • Handwriting expert – established the fundamental principles of document examination.

  • Wrote Questioned Documents

Hans gross
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
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
Edmond Locard

Father of Forensics

  • 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

Essential question2
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?


  • 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
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


  • 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
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


  • 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


  • 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
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 cont1
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 cont2
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 question3
Essential Question

  • What is the role of the forensic scientist?

  • What is the role of the crime scene investigator?

Forensic scientists
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
Crime Scene Investigator

  • Recognize, collect, preserve evidence

Essential question4
Essential Question

  • What are different careers in Forensic Science?


  • 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
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 cont1
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 question5
Essential Question

  • What is evidence?

  • What are the types of evidence?

  • What is the difference between individual and class evidence?


  • Something that tends to establish or disprove a fact

    • Examples

      • Documents

      • Testimony

      • Other objects

Types of evidence
Types of Evidence

  • Evidence

    • Testimonial

      • Expert

      • Eyewitness

    • Physical

      • Individual

      • Class

Expert witness
Expert Witness

  • Person who is a specialist in a subject

  • Only witness who can give their opinion


  • 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


  • 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
Class Evidence

  • Consistent with a particular source

  • The more class evidence that fit the criminal – the better

    • Hair

    • Fibers

    • Soil

    • Glass fragments

Circumstantial evidence
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 question6
Essential Question

  • How can the probative value of class (identified) evidence be increased?

Class evidence1
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 evidence
Probability and Class Evidence


  • 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 evidence1
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 evidence2
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 evidence3
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 evidence4
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 evidence5
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 evidence6
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 evidence7
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
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.