The trouble with DNA testing is that it is so accurate that in effect it's infallable - but that is only true if the lab work is impeccable, and if the police work has been impeccable too.

This means there is a real possibility of juries convicting because they rely on the infallable test, but without allowing for the fallable people who carried out the test, and the sloppy (or worse) procedures that perhaps contaminated the evidence.

It's analogous to the recent case where a woman who had been jailed in England after being convicted for the murder of her two babies was eventually released, when it turned out that the "expert" who had told the court that the possibility of the children having died naturally was many many millions to one against, and that evidence that the children had in fact been suffering from a severe and potentially fatal infection had been suppressed by the prosecution.