Low Copy Dna

[Katoninelive]

Can you tell what sort of dna it is on a slide, blood? sweat? etc using this low copy number technique?

[theprof]

No. A LCN result will not provide information about the type of body fluid the DNA came from. On the other hand, this information may be inferred via the source of the sample. For example, there's a good chance that a sample sourced from a bedsheet is semen.

If you're interested in this Google John Lowe's involvement in the McCann case. There was an initial suggestion that the LCN technique might be usefully applied to a hired vehicle involved in the case, but John Lowe, a leading UK forensic service scientist made it clear LCN techniques would be inconclusive due to the prevalence of key DNA components in the population as a whole

[theprof]

Sorry, I should have made clear that John's department was asked to establish the origin and type of body fluid the sample came from. The size of the sample meant that the LCN technique was the only one that might work.

[Katoninelive]

It's just that i was at a trial where a forensic scientist working for the prosecution said that it was seman on the slide she had tested through lcn dna. The slide was from a 'Cold Case' 16yrs previous?

[theprof]

Hmm, it's difficult to know for sure but I'll take a guess and say that the slide would have been looked at through a microscope before the forensic scientist got hold of it.

Even sixteen year old spermatozoa are still distinguishable distinctively on a slide assuming that the slide had been kept in the conditions needed for future forensic examination. They can't be mistaken for anything else even at that age.

The chances are that the microscopical report would have told her it was semen even before she used the lcn technique. The Court would not have heard that the slide had been examined microscopically unless it was pertinent to the expert evidence submissions.

[Katoninelive]

Thanks for your help theprof