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Principles of Forensic DNA for Officers of the Court

Evidence Screening

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Photo of scientist at table with bags of DNA Evidence
National Institute of Justice (NIJ) (see reuse policy).

The first step performed in the laboratory is the screening of the evidence. The evidence is inventoried, documented, and evaluated for useful biological evidence. Once stains or other biological material of interest are located, they may be subjected to presumptive and confirmatory testing in an attempt to identify the type of biological material present (e.g., blood, semen, saliva).

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