dna

[jannyneve]

is it possible for a person to have a 9 loci dna match to a member of their family,thank you.

[jake-the-peg]

looking at this web site

http://forensic-evidence.com/site/EVID/EL_DNAe rror.html

There is a case og a 6 loci error that was resolved at 10 loci.

The national DNA data base used to use a 6 loci match estimated at 1 in 50 million and now uses a 10 loci match estimated at 1 in 1,000 million.

The 10 loci test is also used in paternity tests where it's rated at in excess of 99.9% accurate

So I find it interesting that you ask about a 9 loci match. Is this not relating to the UK?

I guess from this it's possible but very unlikely

[jannyneve]

hi,thanks for your answer,the reason im asking is someone i know was convicted on a 9 loci test,the person is now hoping for an appeal and the family are soon to be dna tested,and yes it is the uk

[dawkins]

Hi Jenny

Are you talking about crime or paternity?

http://www.lawlink.nsw.gov.au/lawlink/pdo/ll_p do.nsf/pages/PDO_dnadefencelawyers

According to the website above, there has never been a match above seven loci (in new south wales at least). But they do not mention identical twins who would be, er, identical. So a DNA match at 9 loci for a suspect with other good corroborating evidence would be pretty safe but never say never.

D

[jake-the-peg]

Hmm I wonder why it was a 9 and not 10 loci match.

Do you know if the sample was amplified using PCR ? (Polymerase chain reaction)

This is used when a sample is very small and basically reproduces the sample to a size which is testable. This can be quite contraversial due to errors that can be amplified too.

This is the sort of problem that brought the OJ Simpson case crashing down. But things have moved on from 10 years ago.

There's a discussion about it here under PCR contamination

www.scientific.org/tutorials/articles/riley/riley.html

I'd be pretty surprised if a 9 loci test with a good sample falsely identified him.

[dawkins]

Of course, there are other modes of defence:

The DNA evidence alone would not be sufficient for a conviction so if there are other factors such as an alibi there could be grounds for an appeal.

there could be errors in the sampling of the DNA such as amplification errors or contaminated samples which gave erroneous results

there could also have been procedural errors or the crime scene could have been contaminated, again to give erroneous results.

there could be legitimate reasons why the DNA was found at scene not relating to a crime.

D