 Suppose an expert testifies that the crime traces genetically match the defendant and that the random match probability is extremely low, say 1 in 100 million. The random match probability—often interpreted as the probability that someone who is not the source would coincidentally match, \(\Pr(\match \pmid \neg \source)\)—is a common measure of the strength of a DNA match. The lower this probability, the more strongly incriminating the match. Strictly speaking, a match is strong evidence that the defendant is the source only if the likelihood ratio