1 Types of Evidence “You can observe a lot just by watching.” -Yogi Berra, former N.Y. Yankees catcher & sage

2 Evidence Something that tends to establish or disprove a fact.

3 Classification of Evidence 1. Testimonial evidence (Direct): statement made under oath −e−eyewitness account (saw, heard, or did) −P−Police dashboard camera −C−Confessions −N−Not the same thing

4 2.Circumstantial or Real indirect, implies a fact or event a). Physical evidence: any object or material that is relevant in a crime −“real” evidence −Examples:hair, fiber, fingerprints, documents, blood, soil, drugs, toolmarks, impressions, glass −physical and chemical properties

5 Circumstantial Evidence b) Biological Evidence body fluids hair reduce the number of suspects to a likely individual c) Trace Evidence

6 Reliability of Eyewitnesses As a result of the influences on eyewitness memory, physical evidence becomes critical.

7

8

9 Reliability of Eyewitnesses Factors that affect accuracy: −Nature of the offense and the situation in which the crime is observed −Characteristics of the witness −Manner in which the information is retrieved As a result of the influences on eyewitness memory, physical evidence becomes critical.

10 Reliability of Eyewitnesses 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 As a result of the influences on eyewitness memory, physical evidence becomes critical.

11 Physical Evidence Is generally more reliable than testimonial evidence 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

12 Reconstruction Physical evidence can be used to answer questions about: −What took place at a crime scene −The number of people involved −The sequence of events

13 Reconstruction A forensic scientist compares the questioned (Q) (unknown) sample from the crime scene with a sample of known (K) origin.

14 Types of Physical Evidence Transient evidence Pattern evidence Conditional evidence Transfer evidence Associative evidence

15 Transient Evidence Temporary Easily changed or lost Usually observed by the first officer at the scene. −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

16 Pattern Evidence Produced by direct contact between a person and an object or between two objects Mostly in the form of imprints, indentations, striations, markings, fractures, or deposits Clothing or article distribution Gunpowder residue Material damage Body position Toolmarks Modus operandi Blood spatter Glass fracture Fire burn pattern Furniture position Projectile trajectory Tire marks or skid marks

17 Conditional Evidence Produced by a specific event or action Important in crime scene reconstruction, determining circumstances or event sequence indirect evidence Light—headlight, lighting conditions, lights on or off 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, odometer mileage Body—position and types of wounds; rigor, livor, and algor mortis Scene—condition of furniture, doors and windows, any disturbance or signs of a struggle

18 Individual vs. Class Evidence Individual—can be identified with a particular person or a single source Class—common to a group of objects or persons relies on statistics! Blood DNA Typing Fingerprints

19 Individual vs. Class Evidence Individual Evidence Really high probability of being linked to one, unique source Ex: –Fingerprints 1 x 1060 = probability of 2 people having same fingerprint –DNA –Bullets –Tire/ footwear patterns –Tool marks –Broken glass Class Evidence Object has characteristics common to a group of similar objects Ex: –Hair –Fibers –Blue jeans Can increase the probability of class evidence by finding things that can make it unique: –Ex: stains, wear patterns on jeans

20 Individual vs. Class Evidence The large piece of glass fits exactly to the bottle; it is individual evidence. These fibers are class evidence; there is no way to determine if they came from this garment.

21 Individual vs. Class Evidence Which examples do you think could be individual evidence?

22

23 Classroom Activity 1.What time did the intruder come in? 2.What did the intruder look like? Height? Weight? Age? Hair color? Hairstyle? 3.Describe what the intruder was wearing. 4.What conversation took place? 5.Did you see the gorilla?

24 Classroom Activity 1.What time did the intruder come in? 2.What did the intruder look like? Height? Weight? Age? Hair color? Hairstyle? 3.Describe what the intruder was wearing. 4.What conversation took place? 5.At what time did the phone calls take place? How long did they last? What was said? 6.What was the date on the board at the beginning of class?

25 Transfer Evidence Produced by contact between person(s) and object(s), or between person(s) and person(s).

26 Associative Evidence Something that may associate a victim or suspect with a scene or with each other; e.g., personal belongings.

27 Classification of Evidence by Nature Biological—blood, semen, saliva, sweat, tears, hair, bone, tissues, urine, feces, animal material, insects, bacteria, fungi, botanical material Chemical—fibers, glass, soil, gunpowder, metals, minerals, narcotics, drugs, paper, ink, cosmetics, paint, plastic, lubricants, fertilizer Physical—fingerprints, footprints, shoeprints, handwriting, firearms, tire marks, toolmarks, typewriting Miscellaneous—laundry marks, voice analysis, polygraph, photography, stress evaluation, psycholinguistic analysis, vehicle identification

28 Steps in a Forensic Investigation 1.Recognition 2.Preservation 3.Identification 4.Comparison 5.Individualization 6.Interpretation 7.Reconstruction

29 Steps in a Forensic Investigation Recognition of evidence −the ability to distinguish important evidence from unrelated material −pattern recognition −physical property observation −information analysis −field testing Preservation of evidence −collection −proper packaging

30 Steps in a Forensic Investigation Identification of evidence: scientific testing of… −physical/chemical properties −morphology −biological and immunological properties Comparison of evidence −class characteristics 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

31 Steps in a Forensic Investigation Individualization of evidence −demonstrating that the sample is unique, even among members of the same class Interpretation of evidence −giving meaning to all the information Reconstruction of the crime −Inductive and deductive logic −Statistical data −Pattern analysis −Results of laboratory analysis