Unicorns killed President Kennedy!
"The probability of a false positive is as close to nil as makes no odds to your human sample. "
it's something like 1 in 113 billion against an individual, so 153 people in 6 million have duplicate entries, a lot more in 60 million (much much higher than x10), a heck of a lot more in 6 billion people, but then we would only have our little snapshot of those samples.
Still pretty good right? You have a DNA match it's still no worse than say 1000 in 60 million, or 1 in 60000 worst case. All pretty good, and most likely much better, more like 1 in 113 billion if you start with the suspect and then match the DNA, rather than starting with the DNA.
So you've established 'opportunity' because the DNA matches, to within 1 in 60000 or better. Except you haven't, you've established the person was there before during or after which is not opportunity. Since DNA matches pretty well after say 2 months (they survive far better than fingerprints) and say 1000 people are a crime scene in those 2 months, you've got 1 in 6000 or better.
Never mind, it's still pretty good. 1 in 6000.
Now all we need is motive, dig a database till you find some motive, here we are, person X said he hates people who think Y, and person Y once said he thinks Y. Good enough. If I started with the person, then that would likely be a probability of 1 in 100 billion! However I didn't I started saying 'can we prosecute this person' and then found something to prosecute with.
Did unicorns kill President Kennedy?
The search [unicorns kill President Kennedy] has 26700 matches, those murderous unicorns, why? What did Kennedy ever do to you?
You see it all changes when we start with our method to obtain the suspects list. My bet is that the unicorns did it. We need a database of Unicorn DNA quickly!