Originally posted by reg1965
View Post
Why do you say samples need to be frozen? That link you gave before Xmas says quite clearly that DNA is inherently stable and needs something to trigger degredation.
It is not possible to detect where DNA came from or when it came in contact with a particular surface by any transfer method using any DNA testing technique.
So therefore contamination is not purely isolated to blank controls.
It may have been transferred to the sample exhibit before the lab even sees it or after the blank has been set up.
It could even be in the reagent used.
This does not even take into account stochastic effects that occur unpredictably when the amount of template is below the stochastic threshold. This is around 125pg of original template DNA. LCN is always used when template levels are lower than this for obvious reasons.
KR,
Vic.


Moreover, if unrelated DNA is ‘often’ detected by this technique, the fact that it wasn’t in this case doesn’t exactly support an argument for the hanky or knickers being subjected to wanton mishandling or careless storage procedures. Alarm bells might have rung had Hanratty’s DNA turned up among several completely unrelated profiles, but it seems to have stood out like a sore thumb, with only the victim’s - and that attributed to her lover - for company. I don’t see how that could be accounted for by contamination OR degradation; luck, guesswork or gross incompetence. And I don’t recommend blaming it on blatant manipulation and dishonesty either. 
Comment