EVIDENCE CLASSIFICATION OF EVIDENCE Testimonial Evidence: statement made under oath direct evidence eyewitness evidence* 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 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
Additional factors: Witnesss 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 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 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 A forensic scientist compares the questioned (Q) (unknown) sample from the crime scene with a sample of known (K) origin. TYPES OF PHYSICAL EVIDENCE Transient evidence Pattern evidence
Conditional evidence Transfer evidence Associative evidence TRANSIENT EVIDENCE Temporary Easily changed or lost Usually observed by the first officer at the scene. Examples: Odorputrefaction, perfume, gasoline, urine, burning,
explosives, cigarette or cigar smoke Temperaturesurroundings, car hood, coffee, water in a bathtub, cadaver Imprints and indentations footprints, teeth marks in 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 Blood spatter Glass fracture Fire burn pattern Furniture position Projectile trajectory Tire marks or skid marks Clothing or article distribution Gunpowder residue Material damage
Body position Toolmarks Modus operandi PATTERN EVIDENCE CONDITIONAL EVIDENCE Produced by a specific event or action Important in crime scene reconstruction, determining circumstances or event sequence indirect evidence
Smokecolor, direction of travel, density, odor Vehiclesdoors locked or unlocked, windows opened or closed, radio off or on, odometer mileage Firecolor and direction of the flames, speed of spread, temperature and condition of fire Bodyposition and types of wounds; rigor, livor, and algor mortis
Locationof injuries or wounds, of bloodstains, of the victims vehicle, of weapons or cartridge cases, of broken glass Scenecondition of furniture, doors and windows, any disturbance or signs of a struggle Lightheadlight, lighting conditions, lights on or off TRANSFER EVIDENCE
Produced by contact between person(s) and object(s), or between person(s) and person(s). ASSOCIATIVE EVIDENCE Something that may associate a victim or suspect with a scene or with each other; e.g., personal belongings. CLASSIFICATION OF EVIDENCE BY NATURE Biologicalblood, semen, saliva, sweat, tears, hair, bone,
tissues, urine, feces, animal material, insects, bacteria, fungi, botanical material Chemicalfibers, glass, soil, gunpowder, metals, minerals, narcotics, drugs, paper, ink, cosmetics, paint, plastic, lubricants, fertilizer Physicalfingerprints, footprints, shoeprints, handwriting, firearms, tire marks, tool marks, typewriting Miscellaneouslaundry marks, voice analysis, polygraph, photography, stress evaluation, psycholinguistic analysis, vehicle identification INDIVIDUAL VS. CLASS
EVIDENCE Individualcan be identified with a particular person or a single source Classcommon to a group of objects or persons relies on statistics! Fingerprints Blood DNA Typing INDIVIDUAL VS. CLASS EVIDENCE
These fibers are class evidence; there is no way to determine if they came from this garment. The large piece of glass fits exactly to the bottle; it is individual evidence. INDIVIDUAL VS. CLASS EVIDENCE Which examples do you think could be individual evidence?
STEPS IN A FORENSIC INVESTIGATION 1. Recognition 2. Preservation 3. Identification 4. Comparison 5. Individualization 6. Interpretation 7. Reconstruction STEPS IN A FORENSIC
INVESTIGATION 1. Recognition of evidence the ability to distinguish important evidence from unrelated material pattern recognition
physical property observation information analysis field testing 2. Preservation of evidence collection proper packaging STEPS IN A FORENSIC
INVESTIGATION 3. Identification of evidence: scientific testing of physical/chemical properties morphology biological and immunological properties 4. 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 STEPS IN A FORENSIC INVESTIGATION 5.Individualization of evidence demonstrating that the sample is unique, even among members of the same class 6.Interpretation of evidence
giving meaning to all the information 7.Reconstruction of the crime Inductive and deductive logic Statistical data Pattern analysis Results of laboratory analysis
