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Understanding DNA Evidence: A Guide for Victim Service Providers

NCJ Number
Date Published
May 2001
8 pages
Given the importance of DNA evidence in determining the outcome of cases in which it is presented, this guide instructs victim service providers in the nature and importance of DNA evidence in their clients’ cases.
DNA (deoxyribonucleic acid) is first characterized as the “building block” for the human body, with virtually every cell containing it; and DNA does not change throughout a person’s life. An explanation of the value of DNA evidence in criminal investigations notes that, with the exception of identical twins, no two people have the same DNA evidence; therefore, DNA evidence collected at a crime scene can be matched with the DNA of a suspect in order to place him/her at the crime scene, albeit without being able to determine when the DNA was deposited at the crime scene. If the DNA cannot be matched to any known suspect, a crime-scene DNA profile can be entered into the FBI’s Combined DNA Index System (CODIS) in order to determine whether it matches the DNA of any person included in CODIS. The collection of DNA at a crime scene and potential associated problems are discussed, with attention to sexual assault cases. A separate section of the guide addresses contamination and preservation issues for crime-scene DNA samples. The forensic analysis of DNA samples and the interpretation of the analysis are them explained, along with the role of DNA evidence in old, unsolved cases and in post-conviction cases. The guide concludes with the presentation of a list that identifies some areas of a crime scene or on the victim that may contain valuable DNA evidence. Suggested resource organizations and publications

Date Published: May 1, 2001