Types of Evidence

Types of Evidence Evidence can be divided into two types of evidence Direct evidence – evidence in the form of a statement made under oath, such as a witness pointing to a person in a court saying “that’s the guy who robbed the grocery store.” Also known as testimonial evidence.

Types of Evidence Evidence can be divided into two types of evidence Physical evidence – any object or material that is relevant in a crime Almost any tangible thing, as large as a plane, as small as hair, as fleeting as an odor, or as obvious as a demolished building.

Locard’s principle Edmond Locard, a French Forensic Scientitst: Always an exchange or transfer of material when two objects came into contact.

Types of Common Physical Evidence Drugs and toxic substances Paints Gunshot residues Firearms and ammunition Impressions (shoes, teeth) Petroleum products Alcohols (especially ethanol) Rubber material Resins, plastics Explosive residues Serial numbers documents fibers, Soil, glass Blood body fluids Fingerprints Hair Tissues Pollen Wood material Feathers bones

Types of Evidence Most evidence does not prove a fact and is termed indirect evidence. Some physical evidence, however, may be considered proof of fact, such as possessing a controlled substance or a driver’s blood alcohol level of greater than 0.10%.

Types of Evidence Circumstantial evidence – implies a fact or event. The greater volume of circumstantial evidence there is, the greater the weight it carries. Probability and statistics come into play here.

So, What Good is Evidence? Physical evidence can Prove that a crime has been committed Corroborate testimony Link a suspect with a victim or with a crime scene Establish the identity of persons associated with a crime Allow reconstruction of events of a crime

Rules of Evidence Define what evidence is acceptable (admissible) and how it can be used for the jury. Evidence must be relevant, meaning it must prove something (probative) and address the issue of the particular crime (material).

Rules of Evidence Evidence is admissible if it is reliable and the presenter of such evidence is credible and competent. Generally, hearsay is inadmissible in criminal court because it is not reliable nor was it taken under oath and therefore does not allow for cross-examination. Hearsay is admissible in civil suits.

Two legal decisions Legal decisions that govern the admissibility of scientific evidence: Frye versus United States, 1923 Daubert versus Merrell Dow Pharmaceutical, Inc.

Frye Standard Interpretation of scientific evidence must be given by an expert witness and have gained “general acceptance” in the particular field of study. The court must decide if the questioned procedure, technique, and principles are generally accepted by a meaningful segment of the relevant scientific community. Does not offer guidance on reliability.

Daubert ruling Trial judge must assume responsibility and validity of evidence presented in their court. Guidelines: The scientific theory or technique must be testable. The theory or technique must be subject to peer review and publication. Rate of error or potential errors must be stated. The technique must follow standards. Consideration must be given as to whether the theory or technique has attracted widespread acceptance within a relevant scientific community.

Individual versus Class Evidence Individual – best evidence, can be to a single specific source, so there is no doubt as to what the source of the evidence is. Type of evidence can place a suspect at a crime scene, associate a suspect with a victim, and sometimes even prove who committed the crime. Human characteristics that can be linked to an individual are fingerprints, DNA analysis, handwriting voice prints. Individualization always involves comparison.

Individual versus Class Evidence Class evidence is evidence found to be consistent with a particular source. Class evidence alone may or may not be very convincing in a crime, but if there are many different types or pieces of class evidence, the value can be considerable. Class evidence is associated with a group or class, like polyester or blue polyester shirts. Examples of class evidence are hair, fibers, soil, and glass fragments.