1/24/2017 CHAPTER 2 TYPES OF EVIDENCE Classification of Evidence testimonial evidence • a statement made under oath (direct evidence) OBJECTIVES physical evidence You will be able to: • any object or material that is relevant in a crime (indirect evidence) • Explain the difference between indirect and direct evidence. • hair, fiber, fingerprints, documents, blood, soil, drugs, tool marks, • Describe what is meant by physical evidence and give examples. impressions, glass… • Distinguish individual evidence from class evidence. • Determine the significance of class evidence Reliability of an Eyewitness eyewitness accounts can provide important evidence leading to the arrest of a criminal juries are heavily influenced by eyewitness ID Physical Evidence Factors that affect accuracy: nature of the offense and the situation in which the crime is is generally more reliable than testimonial evidence observed can prove that a crime has been committed characteristics of the witness – victims of serious crimes sometimes can corroborate or refute testimony have a more accurate memory (tend to relive the event) can link a suspect with a victim or with a crime scene manner in which the information is retrieved (open ended questions) can establish the identity of persons associated with a crime witness’s prior relationship with the accused can allow reconstruction of events of a crime length of time between the offense and the identification as a result of the influences on eyewitness memory, physical A police composite may be developed from the evidence becomes critical… witness testimony by a computer program or forensic artist. Types of Physical Evidence Transient evidence is temporary; easily changed or lost; usually Physical evidence can be used to answer questions about: observed by the first officer at the scene (odor, temperature, imprints) what took place at a crime scene the number of people involved the sequence of events reconstruction of the crime scene… Pattern evidence is produced by direct contact between a person and an object or between two objects (blood splatter, gun powder residue, body placement, glass fracture, fire burn pattern) 1 1/24/2017 Conditional evidence is produced by a specific event or action (light, smoke, fire, location, vehicles, body, scene) Classification of Physical 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, Transfer evidence is produced by contact between a person and an drugs, paper, ink, cosmetics, paint, plastic, lubricants, fertilizer object or between two people (Lochard principle) physical - fingerprints, footprints, shoeprints, handwriting, firearms, tire marks, tool marks, typewriting miscellaneous - laundry marks, voice analysis, polygraph, Associative evidence is something that may associate a victim or photography, stress evaluation, psycholinguistic analysis, vehicle suspect with a scene or with each other (personal belongings) identification Indirect evidence: evidence that does not prove a fact – evidence CSI’s collect physical evidence and submit to crime lab for testing providing only a basis for inference about the disputed fact role of forensic scientist – determine if there are links among the evidence, the victim, the crime scene and the suspect – is the circumstantial evidence: evidence based on suggestion rather than evidence relevant to the crime… personal knowledge or observation – implies a fact or event without questioned / unknown samples (Q) are compared to known samples actually proving it (K) the more circumstantial evidence, the greater weight it carries – use of probability and statistics questioned sample: material that has been collected from a known location but is of unknown origin known sample: material that comes from a proven or known source control sample: material that is similar to the questioned and known samples and is used to validate the test method and the procedure – expected to respond in a particular way during testing Evidence Characteristics Forensic Investigations include some or all of these seven major activities: individual - can be identified with a particular person or a single source (fingerprints, DNA, handwriting, sometimes physical matches recognition - the ability to distinguish important evidence from (broken glass that fits back together)) unrelated material preservation through the collection and proper packaging of evidence identification using scientific testing class – most evidence - common to a group of objects or persons, but not one object / person (fibers, ABO type, tool marks, shoe comparison of class characteristics measured against those of patterns) 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 individualization in demonstrating that the sample is unique, even among members of the same class 2 1/24/2017 interpretation - giving meaning to all the information reconstruction of the events in the case • inductive and deductive logic • statistical data • pattern analysis • results of laboratory analysis 3.