Identifying DNA Evidence

comparison Since only a few cells can be sufficient to obtain useful DNA information to help your case, the list below identifies some common items of evidence that you may need to collect, the possible location of the DNA on the evidence, and the biological source containing the cells. Remember that just because you cannot see a stain does not mean there are not enough cells for DNA typing. Further, DNA does more than just identify the source of the sample; it can place a known individual at a crime scene, in a home, or in a room where the suspect claimed not to have been. It can refute a claim of self-defense and put a weapon in the suspect's hand. It can change a story from an alibi to one of consent. The more officers know how to use DNA, the more powerful a tool it becomes


Evidence		 Possible Location of DNA on the Evidence Source of DNA
baseball bat or similar weapon handle, end sweat, skin, blood, tissue
hat, bandanna, or mask inside sweat, hair, dandruff
eyeglasses nose or ear pieces, lens sweat, skin
facial tissue, cotton swab surface area mucus, blood, sweat, semen, ear wax
dirty laundry surface area blood, sweat, semen
toothpick tips saliva
used cigarette cigarette butt saliva
stamp or envelope licked area saliva
tape or ligature inside/outside surface skin, sweat
bottle, can, or glass sides, mouthpiece saliva, sweat
used condom inside/outside surface semen, vaginal or rectal cells
blanket, pillow, sheet surface area sweat, hair, semen, urine, saliva
"through and through" bullet outside surface blood, tissue
bite mark person's skin or clothing saliva
fingernail, partial fingernail scrapings blood, sweat, tissue

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Some or all of the content on this page is excerpted from the online training courses What Every Law Enforcement Officer Should Know About DNA Evidence, developed under an award from the Office of Justice Programs' National Institute of Justice. See award product disclaimer.