Fingerprint evidence has long been considered an infallible form of proof. When three top experts blew the identification in the case of Oregon lawyer Brandon Mayfield, writes U. Virginia law Prof. Jennifer Mnookin in the Washington Post, our faith in fingerprints must be questioned. She notes that in January a Massachusetts conviction was overturned when the fingerprint identification, the cornerstone of the case, was shown to be erroneous.
The science of fingerprinting is surprisingly underdeveloped. We lack good evidence about how often examiners make mistakes, nor is there a consensus about how to determine what counts as a match. Our current approach to fingerprint evidence, in which experts claim 100 percent confidence in any match, is dangerously flawed and risks causing miscarriages of justice, Mnookin says. Until now, many people in the field have resisted calls for research and investigation of fingerprinting. Because experts are permitted to testify about “100 percent positive” matches and to claim in court an error rate for the technique of zero, they have little incentive to support research. No matter how accurate fingerprint identification turns out to be, it cannot be as perfect as they claim.