Cross-contamination of evidence
Cross-contamination of evidence (Forensic Science)
Forensic investigation of a crime scene relies on Locard’s exchange principle, which states that when two objects come in contact, they exchange trace evidence. A crime scene thus contains evidence that may place a suspect at the scene, and analysis of that evidence may reveal the associations between perpetrator and crime that are necessary for a prosecutor to obtain a conviction in a court of law. Evidence may also refute theories that link a suspect to a crime and thus may exonerate the innocent.
The methods used in the collection and preservation of evidence are intended to ensure that the preserved materials did originate from the crime scene, that the materials are pertinent to the crime, and that the materials can be analyzed in a comparable state to the way they were found at the scene. Cross-contamination of evidence results from the failure to protect an evidence sample from the transfer of other material onto or into it. Evidence may become cross-contaminated at the crime scene during collection and packaging of evidential materials, during transportation to laboratories or other facilities, during storage, or while it is undergoing analysis.
At the crime scene, cross-contamination of evidence is most likely to occur when the actions of first responders and others moves materials such as hairs, fibers, and fluids around the scene. Evidence may also be compromised by cross-contamination when investigators do not use crime...
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Further Reading (Forensic Science)
Genge, N. E. The Forensic Casebook: The Science of Crime Scene Investigation. New York: Ballantine, 2002.
Pentland, Peter, and Pennie Stoyles. Forensic Science. Philadelphia: Chelsea House, 2003.
Platt, Richard. Crime Scene: The Ultimate Guide to Forensic Science. New York: Dorling Kindersley, 2003.
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