DNA evidence can provide the IDENTITY (who!) of the crime.
Some examples of DNA evidence:
- Baseball bat/weapon: handle/end (sweat, skin, blood tissue)
- Eyeglasses: Nose or ear pieces/lens (sweat, skin)
- Facial tissue (cotton swab): surface area (mucus, blood, earwax, skin cells!)
- Used cigarette: cigarette butt (saliva)
- Stamp/Envelope: surface area (saliva)
- Blanket/Pillow/Sheet: surface area (sweat, hair, urine, saliva)
- Fingernail: scrapings (blood, sweat, tissue)
*Blood: RBCs cannot be used, as it has NO NUCLEUS
*Urine: Not only DNA, but also traces of drugs, steroids, etc.
What is DNA typing?
A DNA profile is an encrypted set of numbers that is an "identifier" (like a barcode!). DNA typing uses highly variable repetitive sequences, like VNTRs (variable number tandem repeats) and STRs (short tandem repeats). These can be similar in related people, but VERY different in unrelated ones.
*Polymerase Chain Reaction: Method of amplifying a single/few copies of a piece of DNA.
DNA test results first allowed to be used as evidence in 1990.
- RISK: DNA typing risks perpetrating injustice by focusing only on physical evidence in a trial
- Why?: DNA typing only tests several areas of the DNA (the only 100% sure way is to test all 23 pairs of chromosomes)
- One in 100,000 or 1,000,000 probability of two people sharing the same results.
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