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Expert witnesses will often quote numbers like that in court, stating that the probability of a random person getting a DNA match is less than 1 in (some large
by capnrefsmmat 11y ago
Expert witnesses will often quote numbers like that in court, stating that the probability of a random person getting a DNA match is less than 1 in (some large number) million.
However, the FBI has been strongly resistant to opening up their DNA databases so these numbers could actually be verified empirically. (I think currently they just multiply some numbers together to get an estimate.) Some preliminary research suggests that partial DNA matches are much more common than claimed.
Here's a law review article about the problem: http://papers.ssrn.com/sol3/papers.cfm?abstract_id=1551467 http://papers.ssrn.com/sol3/papers.cfm?abstract_id=1551467
Naturally it suffers from the common law review problem that most of its text is in footnotes instead of the main body, but it's pretty good...
- sukilot 11y agoThe math is still wrong! A million to one odds and a full USA population database means the 300 people are perfect matches, open and shut convictions! There was famous case that actually won (for the good guys) by taking this math to court. These forensic anyalses do bad statistics (wildly wrong priors) and compute wildly wrong posteriors.
- capnrefsmmat 11y agoThat's true, but they'll often report random match probabilities like "one in 930 sextillion", which are absurd. Do you have a reference to the case you mention? I'd like to read the history of it.