Wednesday 5/29/13

• AIM: how can we be successful on our post assessment exam?

• DO NOW: Grab a text book and define criminalistics and evidence.

• Explain the difference between class and individual characteristics

• HOMEWORK: Review sheet

• a shoe print is left at a burglary scene. Identify each of the following as individual or class characteristics.– Manufacturer of shoe– Pattern of print– Sole imprint– Size of shoe

Criminalitics

• the application of science to the physical evidence

• bloodstains

• DNA

• bullet trajectories – includes the psychological angle– studying crime scenes for motives, traits,

and behavior.

Evidence:establishes or disproves a fact

– Testimonial Evidence – Any witness accounts of the crime– Physical– any material items that would be present on

the crime scene– Hard evidence left at the crime scene– Fingerprints, blood or semen samples, hair

samples etc.

Individual vs Class

• Individual evidence: can be connected to one single person– DNA, fingerprints, hair if there is a follicle,

glass, bite marks

• Class evidence: related to an entire group– Glass, hair, blood

Locard’s Exchange Principle –

• It was Locard’s belief that when a criminal came in contact with an object or person, a cross-transfer of evidence occurred.

• The exchange of materials between two objects that occurs whenever two objects come into contact with one another.

Crime Labs

– 1915: Edmond Locard– Lyon France– His only instruments were a microscope and

spectrometer– 1923: Los Angeles Police Department– First Crime lab in the US– Current Day FBI has the LARGEST crime lab

in the WORLD

United States crime labs

• Currently there are 320 in the US alone– Operate on different levels– Federal– State– County– Municipal– Crime Labs may function as part of the police

department or the District Attorney’s office– Medical examiner or coroner

Criminalist or Forensic analyst

• JOB is to analyze evidence and testify about the facts– Provide an expert opinion– NO BIAS NO OPINIONS

• 1960’s supreme court began depending on scientific evidence

• 1990’s DNA profiling was discovered– Creation of a National DNA profile system

• Today FBI has the largest forensics lab in the world

Legal terms to know

• Stare decisis

• Corpus delecti

• Nolo contendere

• Pro bono

• Corpus delicti: the principle that a crime must have been proven to have occurred before a person can be convicted of committing that crime.

• Stare decisis: "the decisions remains" or words to that effect, It says that once a decision is made it becomes a precedent and the courts have a bias toward respecting and preserving that precedent. It is necessary to ensure that the law be predictable and consistent and not change every time a different judge or bench looks at an issue

• Pro bono: work taken voluntarily.• Nolo contendere: refers to a pleas of no contest.

An alternative to pleading guilty or not guilty.

Crime Scene Analysis

• 1- Seal off the crime scene

• 2- each piece of evidence is packaged separately

• 3-begin to mentally document the scene

• 4- check the body if there is one

• 5- isolate witnesses

• 6- observe the scene for evidence

Maintain a chain of custody

• A list of each person who comes in contact with the evidence

• Makes sure evidence is not tampered with in order to be admitted into court

• NO CHAIN OF CUSTODY NO COURT ADMISSION

Branches of a crime unit

– Physical Science Unit• Chemistry• Drug test

– Biomolecular evidence• Physics

– Trajectory• Geology• Soil• Rocks• mineral

Basic services of a crime unit

• Biology

• Firearms

• Questioned document: checks, diacritics

• Photography

• Odontology

• Latent fingerprint

• Polygraph

diacritics

• marks such as an accent or a tilde that indicate the correct pronunciation of a letter or combination of letters which, without the mark, would be pronunced differently.

• Crossing of t dotting of i

Optional Services of a crime unit

– Toxicology unit• Usually under the medical examiners direction• Drugs,alcohol, poisons• Fingerprint unit• Polygraph unit

– Voiceprint analysis– Telephone threats or taped messages– Voiceprint: transforms speech into visual graphic– Evidence Collection unit– Cyber bullying

• Voiceprint Analysis Unit - The sound spectrograph is an instrument that transforms speech into a visual graphic display called a voiceprint.

Forensic entomology

• Observes the development of bugs

Forensic Pathology -

• This field involves the investigation of sudden, unnatural, unexplained, or violent deaths,disease

• Rigor mortis

• Algor mortis

• Liver mortis

1- Algor Mortis: Time of death

• Check the body core temperature

• At the scene, a thermometer is inserted into the liver

• Body temperature drops about one degree Celsius per hour after death

1- Algor Mortis Time of death continued

• Body Temperature cools until it reaches room temperature

• Rate of cooling is determined by– Location and size of body– Victim’s clothing– Weather conditions– General rule; body looses 1-1.5 degrees

every hour

2- Stiffening of the body

• Rigor Mortis: Muscles relax and then become rigid

• Joints of body stiffen and lock– Sets in within 30

minutes to 3 hours after death

– Goes away 24-36 hours after it begins

3- Liver Mortis• Blood settles in parts of the body closest to

the floor

• Happens 6 hours after death

• More efficient in determining cause of death

Forensic anthropology

• Analyzes bones– Age, sex, race, height NOT weight

• Sutures: determine age

Fingerprints

• Should be developed within 24 hours of the crime, found on any surface NOT ON A BODY

• 3 types of prints• Visible, plastic, latentFingerprint patterns

Loops whorls arches% in general

population 60 - 65 30 - 35 5

Visualizing a human fingerprint

• MOST REACT with sweat oils• Development is based on the surface it is found

on• Cyanoacrylate ester: found in super glue• Can visualize a print on a porous surface• Ninhydrin: white powder or clear liquid

– Reacts with the amino acid in skin– Turns purple when amino acid is present

• Iodine: drawback is when the vapors disappear the print disappears

Hairs and fibers

• Human hair characteristics

• Cuticle

• Cortex

• Medulla: 1/3 of the hair shaft diameter other animals about 1/2

• ACT: anagen, catagen, telogen

Fiber patterns

• Wayne Williams

Natural fibers are derived in whole from animal & plant sources

Coton, wool

REGENERATED FIBERS - use CELLULOSE from plant materials mixed with a solvent to produce a fiber

rayon, acetate, triacetate

Drugs

• Analgesics: relieve pain

• Spot tests

• Blood alcohol content: alcohol is dissolved in the blood and leaves the body unchanged in breath, sweat and urine

COLOR TESTS: for screening only

A drug is mixed with a reagent which turns colors.

Bullet caliber

• Caliber is a measurement of the diameter of the gun

Human blood

• Class characteristic

• Determined by the antigen present– 3 alleles but only 2 antigens

• Blood type A has antigen A

• To determine if a sample is human, precipitin tests are used– Basically antigen antibody response

Fire: parts of a fire

• Fuel + oxygen= carbon dioxide, water, heat and flame

Terms to know

• CODIS: Combines DNA Index System

• AFIS: Automated Fingerprint Identification system

• IBIS: Integrated Ballistics

• IAFIS: Integrated Automated Fingerprint

Chromatography

• Capillary action

• Retention time

• Rf value

KNOWN SAMPLES

UNKNOWN SAMPLES

KNOWN QUININE

KNOWN HEROIN

Rf - a value given to the distance traveled by each compound. Somewhat unique to the compound.

Comparison Microscope

• Used to compare unknown samples to known samples

• Places samples side by side