Mayfield, 37, an Oregon lawyer and Muslim convert, was arrested as a material witness after the devastating terrorist train bombings that rocked Madrid in March 2004. The FBI’s Integrated Automated Fingerprint Identification System turned up 20 possible matches to a partial print on a plastic bag of detonator caps found nearby. Three FBI agents were certain that Mayfield’s prints, in the system after a teenage arrest, were a match. Mayfield’s court-ordered, independent expert concurred.
While Mayfield spent two weeks behind bars, skeptical Spanish authorities chased other leads, ultimately determining that the print belonged to an Algerian, Ouhnane Daoud. Chastened, the FBI backed down and even apologized to the Mayfield family. Mayfield, who was sure he was targeted because of his faith, was later awarded $2 million in damages.
In another study, his team had six international experts each view eight latent prints that they’d each previously examined, but now they were accompanied with a new, mundane context — something like, “the suspect has confessed,” or, “the suspect is in custody.” More expert reversals followed. Four of the six reached different conclusions. One changed his mind three times.I'm somehow both amazed and not surprised at all that fingerprint examiners are allowed to know the details of the case they are working on or how other examiners have decided.