Introduction to Forensic Science and the Law Federal Rules of Evidence In order for scientific evidence to be admitted in a court of law, it must be: a) Probative: actually proves something b) Material: addresses an issue that is relevant to the particular crime

Introduction to Forensic Science and the Law Admissibility of Evidence The Frye Standard From the 1923 case Frye v. United States Standard used for determining if scientific evidence may be presented before the court. The standard states that the court will accept expert testimony on “well recognized scientific principle and discovery’ if it has been “sufficiently established and has received general acceptance” in the scientific community

Introduction to Forensic Science and the Law Admissibility of Evidence The Daubert Ruling From the 1993 case Daubert v. Merrell Dow pharmaceuticals The judge may use expert testimony to “understand evidence” and decide if the evidence can be entered into the trial. Admissibility of new scientific technique or theory is determined by: be subject to testing and peer review Be standardized with recognized maintenance of such standards Have a known and accepted error rate Attain widespread acceptance

Introduction to Forensic Science and the Law Using Evidence Evidence is used to: determine if a crime has been committed link a suspect to a crime scene corroborate or refute an alibi or statement identify a perpetrator or victim exonerate the innocent Induce confession Direct further investigation

Introduction to Forensic Science and the Law Using Evidence Crime scene evidence is valued for the following: Corpus Delicti-Latin term which means “the body of the crime” or the essential facts of the crime. Evidence will reveal exactly what type of crime was committed Modus operandi (MO)-The steps and method (usually repetitive) the perpetrator employed to commit the crime

Introduction to Forensic Science and the Law Using Evidence Crime scene evidence is valued for the following: Linkage-association, or linking of a suspect to a crime scene, or victim Verification-substantiate or refute suspect or witness statement Suspect Identification-evidence such as fingerprint and DNA can often identify the perpetrator

Introduction to Forensic Science and the Law Using Evidence Increasing the value of class evidence involves: Finding as many different items as possible with which to link the suspect to the crime or victim Use the product rule (statistical analysis) to narrow down your pool of suspect so that the probability of all those pieces of evidence identifying someone else as the perpetrator of the crime is almost impossible.

Introduction to Forensic Science and the Law Analysis of Evidence Crime scene evidence is analyzed for two reasons: Identification: determines exactly what a particular item or substance is. Comparisons: done to see if suspected items share a common origin or source (did they come from the same person, place, or object).

Introduction to Forensic Science and the Law Analysis of Evidence Evidence that is being analyzed may exhibit: Class characteristics-not unique to a particular object, but can be narrowed down to a specific group Individual Characteristics-unique, can be narrowed to single source to make direct connection (DNA, Fingeprint)

Introduction to Forensic Science and the Law Analysis of Evidence Class evidence can be individualized. Individualizing the evidence eliminates everyone except the perpetrator. Evidence is intended to eliminate suspects rather than point the finger at any one person