[mywittyname]

It also gives them a nice list of potential suspects that they can pin the crime on. A test which is only accurate to about 1 in 300,000 will produce a reasonably large list of people when the tested population is in the 10s of millions.

Prosecutors are going to chose the one that is most easily convicted. And that may or may not be the person who's actually guilty. It will most likely be the one who cracks the most easily under interrogation (read: trusts that the police are "helping them clear things up"). The actually guilty person would think to STFU and get a lawyer; an innocent person is going to think this "honest mistake" will get cleared up.