U N I T 1 F O R E N S I C S C I E N C E

E R L E N B E C K

Intro to Forensics and Types of Evidence

Observation vs. Inference

�  Observation: Use one or more of your five senses to gather information ¡  A noting and recording of ….FACTS!!!! ¡  Give me an example

�  Inference: A logical interpretation based upon prior knowledge and experience. ¡  Based upon observation ¡  Give me an example

Note the differences…

�  In any lab exercise, you record observations, not inferences.

�  Inferences are made when you write your conclusion to the lab exercise.

Make 3 observations and 3 inferences about this picture.

Eyewitness Exercise

�  Choose several people to be observers and choose two people to be investigators.

�  Allow the observers to look at the picture for 30 seconds. The investigators should not look at the picture.

�  After 30seconds,the investigators should begin questioning the observers. Each Investigator should question each observer. Then, the Investigators should attempt to reconstruct the scene based on the "eyewitness testimony".

Forensics is…

� Science as applied to criminal proceedings.

� Not all forensics = DEATH.

Crime Lab History

§  First police crime lab in the world was established in France in 1910 by Edmond Locard

§  First police crime lab in the U.S. opened in 1923 in Los Angeles

§  The Scientific Crime Detection Lab was founded in Evanston, Illinois in 1929

§  The first FBI crime lab opened in 1932

People of Historical Significance

Edmond Locard (1877-1966) §  French professor §  Considered the father of

criminalistics §  Built the world’s first forensic

laboratory in France in 1910 §  Locard Exchange Principle

§  Whenever two objects come into contact with each other, traces of each are exchanged.

Crime Scene Team

§  A group of professional investigators, each trained in a variety of special disciplines.

§  Team Members §  First Police Officer on the scene §  Medics (if necessary) §  Investigator(s) §  Medical Examiner or Representative (if necessary) §  Photographer and/or Field Evidence Technician §  Lab Experts

pathologist serologist DNA expert toxicologist forensic odontologist forensic anthropologist forensic psychologist forensic entomologist firearm examiner bomb and arson expert document and handwriting experts fingerprint expert

Types of Crime

§  Infraction – violation not resulting in prison: traffic, littering

§  Misdemeanor – minor crime: theft, assault, possession of small amt of drugs

§  Felony – major crime: rape, murder, 3rd DUI

Types of Evidence

Two general types: §  Testimonial—a statement made under oath; also known

as direct evidence or Prima Facie evidence

§  Physical—any object or material that is relevant in a crime; also known as indirect evidence. Examples are hair, fiber, fingerprints, documents, blood, soil, drugs, tool marks, impressions, glass.

Reliability of Eyewitness

Factors: §  Nature of the offense and the situation in which the crime

is observed §  Characteristics of the witness §  Manner in which the information is retrieved

Additional factors: §  Witness’s prior relationship with the accused §  Length of time between the offense and the identification §  Any prior identification or failure to identify the defendant §  Any prior identification of a person other than the

defendant by the eyewitness

The Facts

� In this country, it is estimated that 75% of wrongly convicted defendants, later cleared by DNA evidence, were convicted based largely on eyewitness testimony.

Flashbulb Memories

� Many  vic)ms  of  crimes  have  something  that  is  called  a  flashbulb  memory  

�  This  is  a  vivid  recollec)on  of  drama)c  or  emo)onally  charged  events  

�  Example:  Can  anyone  tell  me  what  you  were  doing  when…?  ¡  You  first  saw  or  heard  about  September  11  ¡  Barack  Obama  became  president  ¡  Michael  Jackson  died ¡  Nsync  broke  up  

You Be the Eyewitness

�  Imagine you are at a gas station buying milk

�  A man walks in, threatens the employee at the counter, robs the cash register, and runs out

�  The entire ordeal lasts about five seconds

�  This is the man you saw…

You Be the Eyewitness

�  The police have asked you to help them identify the perpetrator

�  They will show you a set of pictures, and it is your

responsibility to select the picture of the man you saw rob the gas station…

How Did You Do?

�  So, which picture did you choose?

�  And the correct answer was... #2 �  Were you right? �  What does this tell you about eyewitness testimony?

According to Research…

�  Studies show that the longer it takes an eyewitness to decide if the perpetrator is in a lineup, the less confident they actually are about their decision

�  Why? �  Eyewitnesses typically take several minutes to point

out the perpetrator because they often feel pressured to choose the correct one

�  However, if they are truly confident, they should be able to decide in under 10 seconds

Choosing From a Lineup

�  Research from Buckhout (1974) and Wells (1993) indicate that an eyewitness is more likely to falsely identify a person in a set of lineup photographs if there is anything that separates one picture from another

�  For example: ¡  If one picture is larger than the others ¡  If facial features in all the photographs are not identical

Ronald Cotton Case Study

�  hJp://www.youtube.com/watch?v=u-­‐SBTRLoPuo  

�  hJp://www.youtube.com/watch?v=I4V6aoYuDcg&feature=related    

Value of Physical Evidence

§ Generally more reliable than testimonial § Can prove that a crime has been committed § Can corroborate or refute testimony § Can link a suspect with a victim or with a

crime scene § Can establish the identity of persons

associated with a crime § Can allow reconstruction of events of a

crime

Reconstruction

Physical Evidence is used to answer questions about:

§  what took place §  how the victim was killed §  number of people involved §  sequence of events

A forensic scientist will compare the questioned or unknown sample with a sample of known origin.

https://www.youtube.com/watch?v=EPoNOpL8CvY

Types of Physical Evidence

§  Transient Evidence—temporary; easily changed or lost; usually observed by the first officer at the scene

§  Pattern Evidence—produced by direct contact between a person and an object or between two objects

§  Conditional Evidence—produced by a specific event or action; important in crime scene reconstruction and in determining the set of circumstances or sequence within a particular event

Types of Physical Evidence

§  Transfer Evidence—produced by contact between person(s) or object(s), or between person(s) and person(s)

§  Associative Evidence—items that may associate a victim or suspect with a scene or each other; ie, personal belongings

Examples of Transient Evidence

§  Odor—putrefaction, perfume, gasoline, urine, burning, explosives, cigarette or cigar smoke

§  Temperature—surroundings, car hood, coffee, water in a bathtub, cadaver

§  Imprints and indentations—footprints, teeth marks in perishable foods, tire marks on certain surfaces

§  Markings

Examples of Patter Evidence

�  Pattern Evidence—most are in the form of imprints, indentations, striations, markings, fractures or deposits.

§  Blood spatter §  Glass fracture §  Fire burn pattern §  Furniture position §  Projectile trajectory §  Tire marks or skid marks

§  Clothing or article distribution

§  Gun powder residue §  Material damage §  Body position §  Tool marks §  Modus operandi

Examples of Conditional Evidence

§  Light—headlight, lighting conditions §  Smoke—color, direction of travel, density, odor §  Fire—color and direction of the flames, speed of spread,

temperature and condition of fire §  Location—of injuries or wounds, of bloodstains, of the

victim’s vehicle, of weapons or cartridge cases, of broken glass

§  Vehicles—doors locked or unlocked, windows opened or closed, radio off or on (station), odometer mileage

§  Body—position, types of wounds; rigor, livor and algor mortis

§  Scene—condition of furniture, doors and windows, any disturbance or signs of a struggle

Classification of Evidence by Nature

§  Biological—blood, semen, saliva, sweat, tears, hair, bone, tissues, urine, feces, animal material, insects, bacterial, fungal, botanical

§  Chemical—fibers, glass, soil, gunpowder, metal, mineral, narcotics, drugs, paper, ink, cosmetics, paint, plastic, lubricants, fertilizer

§  Physical—fingerprints, footprints, shoe prints, handwriting, firearms, tire marks, tool marks, typewriting

§  Miscellaneous—laundry marks, voice analysis, polygraph, photography, stress evaluation, psycholinguistic analysis, vehicle identification

Evidence Characteristics

§  Class—common to a group of objects or persons

§  Individual—can be identified with a particular person or a single source

Blood DNA Typing Fingerprints

Class vs. Individual Evidence

Which examples do you think could be individual evidence?

Components of Forensic Investigations

Include some or all of these seven major activities 1. Recognition—ability to distinguish important

evidence from unrelated material §  Pattern recognition §  Physical property observation §  Information analysis §  Field testing

2. Preservation—collection and proper preservation of evidence

Components of Forensic Investigations

3. Identification—use of scientific testing §  Physical properties §  Chemical properties §  Morphological (structural) properties §  Biological properties §  Immunological properties

4. Comparison—class characteristics are measured against those of known standards or controls; if all measurements are equal, then the two samples may be considered to have come from the same source or origin.

Components of Forensic Investigations

5. Individualization—demonstrating that the sample is unique, even among members of the same class

6. Interpretation—gives meaning to all the information

7. Reconstruction—reconstructs the events of the case §  Inductive and deductive logic §  Statistical data §  Pattern analysis §  Results of laboratory analysis

Corpus Delicti “Body of the Crime”

�  You must prove ¡  That a crime occurred ¡  That the person charged with the crime was responsible for the crime

�  Top Reasons for Committing a Crime ¡  Money ¡  Revenge ¡  Emotion—love, hate, anger

�  Source of Evidence ¡  Body ¡  Primary and/or Secondary Crime Scene ¡  Suspect(s)

Crime Scene Investigation

�  Based on scientific method and the Locard Exhange Principle, logic and forensic techniques.

�  Involves ¡  Recognition ¡  Identification ¡  Individualization ¡  Reconstruction

Processing a Crime Scene

�  Isolate and secure the scene �  Document the scene �  Search for evidence �  Collect and package evidence, maintaining the chain

of custody �  Submit evidence to the crime lab

First Officer on the Scene

� A Assess the crime scene and assist those hurt � D Detain the witness � A Arrest the perpertrator � P Protect the crime scene � T Take notes

Crime Scene Survey

�  Walk-through: performed by the crime scene investigator, the first officer, and sometimes, the lead detective.

�  Purpose: ¡  Mentally prepare a reconstruction theory ¡  Note any transient or conditional evidence that could change over

time. ¡  Note the weather conditions ¡  Note points of entry or exit, as well as paths of travel within the crime

scene ¡  Record initial observations of who, what, where, when, and how ¡  Identify special needs within the crime scene for personnel,

precautions or equipment and notify superior officers or other agencies.

Documentation

�  Notes: date and time, description of the location, weather and environmental conditions, description of the crime, location of the evidence relative to other key points, the names of all involved, modifications that have occurred and other relevant information

�  Photography: photos of scene and surroundings, mid-range to close-up photos with various angles or each piece of evidence, photos as viewed by the witness

Documentation

�  Sketches: inclusion of date, time, scale, reference points, distance measurements, names of investigators, victims, suspects, and a key

�  Videography: allow narration (non-subjective) to be included.

Search Methods

�  Line or strip method: best in large, outdoor scenes

�  Grid method: basically a double-line search; effective, but time consuming.

�  Zone method: most effective in houses or buildings; teams are assigned small zones for searching.

�  Wheel or ray method: best on small, circular crime scenes

�  Spiral method: may move inward or outward; best used where there are no physical barriers

Crime Scene Sketch

Collecting & Packing Evidence

§  One individual should be designated as the evidence collector to ensure that the evidence is collected, packaged, marked, sealed, and preserved in a consistent manner

§  Each item must be placed in a separate container, sealed, and labeled

§  Most fragile is collected and packaged first §  Different types of evidence require specific or special

collection and packaging techniques §  The body is the property of the coroner or medical

examiner. The collection of evidence on the body is done by that department

Packing

�  Most items should be packaged in a primary container and then placed inside a secondary one. These are then placed inside other containers such as paper bags, plastic bags, canisters, packets and envelopes depending on the type and size of the evidence.

Chain of Custody

There must be a written record of all people who have had possession of an item of evidence. §  The evidence container must be marked for identification §  The collector’s initials should be placed on the seal §  If evidence is turned over to another person, the transfer

must be recorded.

Crime Scene Reconstruction

Stages §  Data collection §  Hypothesis formation §  Examination, testing and analysis §  Determination of the significance of the

evidence §  Theory formulation

Investigators

“The wise forensic investigator will always remember that he must bring all of his life experiences and logic to find the truth. This means common sense, informed intuition, and the courage to see things as they are. Then he must speak honestly about what it adds up to.”

—Dr. Henry Lee Chief Emeritus for Scientific Services and the

former Commissioner of Public Safety for the state of Connecticut

The Medical Examiner and the Coroner

§  A medical examiner is a medical doctor, usually a pathologist and is appointed by the governing body of the area. There are 400 forensic pathologists throughout the U.S.

§  A coroner is an elected official who usually has no special medical training. In four states, the coroner is a medical doctor.

Medical Examiner’s Responsibilities

§  Identify the deceased §  Establish the time and date of death §  Determine a medical cause of death—the injury or disease that resulted

in the person dying §  Determine the mechanism of death—the physiological reason that the

person died §  Classify the manner of death

§  Natural §  Accidental §  Suicide §  Homicide §  Undetermined

§  Notify the next of kin

The Corpse

“The way I see it, being dead is not terribly far off from being on a cruise ship. Most of your time is spent lying on your back. The brain has shut down. The flesh begins to soften. Nothing much new happens, and nothing is expected of you.” —Mary Roach. Stiff. W. W. Norton & Company.

2003