The so-called "50K study" took a set of 50,000 pre-existing images of fingerprints and compared each one electronically against the whole of the data set, producing a grand total of 2.5 billion comparisons. It concluded that the chances of each image being mistaken for any of the other 49,999 images were vanishingly small, at 1 in 1097.
But Meagher's study continues to be severely criticised. Critics say that showing an image is more like itself than other similar images is irrelevant. The study does not mimic what happens in real life, where messy, partial prints from a crime scene are compared with inked archive prints of known criminals. [...]
He wrote that critics misunderstood the purpose of his study, which sought to establish that individual fingerprints are effectively unique - unlike any other person's print. "This is not a study on error rate, or an effort to demonstrate what constitutes an identification."
[...] From these Cole estimates that false matches occurred at a rate of 0.8 per cent on average, and in one year were as high as 4.4 per cent. Even if the lower figure is correct, this would equate to 1900 mistaken fingerprint matches in the US in 2002 alone.
But on CSI, the evidence is never ambiguous, and they always get a confession before the end of the episode! Real life is so unfair!