From the article:<p>&gt; &quot;When they retested it, the likelihood that it could be someone else was, I think, one in 30-something, one in 40. So it was a significant probability that it could be someone else,&quot; Torres says.<p>No. That is the probability that the test would have claimed a match with a particular person, conditioning on it not being the right person. In order to calculate the probability that it was someone else, you need to know the probability of it having been the right person prior to the test being performed. If you take a sample and test it against everyone in a big enough database, with a 1-in-30 false positive rate, then you will definitely end up accusing someone falsely.