low desity dna test.

[jannyneve]

what is meant by a low density dna test?i read somewhere that in america the FBI consider it to be unsafe to use in a court of law,thanks.

[jake-the-peg]

I believe the position is that when only small samples are available something called PCR (Polymerise Chain Reaction) is used to basically duplicate the DNA to a sufficient quantity to be tested.

Unfortunately if there is any sample contamination this is grown too and makes the whole test basically worthless - I think this is what happened in the OJ Simpson trial:

http://www.promega.com/geneticidproc/ussymp6proc/gerdes.htm

As it happens about the same time there was a test case called Daubert v. Merrell Dow Pharmaceuticals, Inc which established guidelines for PCR based DNA evidence but I think that PCR based DNA tests are fertile grounds for appeal so the FBI may have decided not to persue such evidence in court.

I may have totally gotten the wrong end of the stick so I stand to be corrected - I think we have a Forensic Science student so if you're lucky you might get an expert answer!