- #71
~christina~
Gold Member
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ideasrule said:So when the prosecution says "there's a 1 in 4 billion chance that the DNA match is coincidental", what they actually mean is "there's a 1 in 3 chance that the stupid intern contaminated the crime scene DNA with the reference and made the two match". I'm definitely not saying that DNA evidence should be thrown out, just that it's ironic for a greater demand for evidence to lead to more false positives.
The "chance" that is described is all dependant on how it is looked at. It depends on the group (is it the 1/x chance that DNA sample would match someone of x nationality who is female/male in a x location) that is looked at. Sometimes I think they look at all the probabilities and pick the outlier of the group just to make their case look stronger (no one really asks how they get that number).
I'd disagree with the conclusion that "greater demand for evidence" is what is leading to false positives. It's probably due to the lack of actual forensic scientists who actually collect evidence at crime scenes. They just train normal police to do that job which increases the chance for problems.I'm definitely not saying that DNA evidence should be thrown out, just that it's ironic for a greater demand for evidence to lead to more false positives.