Nobody knows how many people sit wrongfully convicted in prison due to errors in fingerprint matching. But a new study suggests there could be a thousand or more unknown identification errors a year in the United States.
Criminologist Simon Cole of the University of California at Irvine examined all 22 known cases of fingerprint mistakes made since 1920.
Most of the 22 cases were revealed only through “extremely fortuitous circumstances,” such as a post-conviction DNA test, the intervention of foreign police and in one case a deadly lab accident that led to the re-evaluation of evidence, Cole said today.
One highly publicized example was the case of Brandon Mayfield, a Portland lawyer held for two weeks as a suspect in the Madrid train bombings in 2004. FBI investigators matched prints at the scene to Mayfield, and an independent examiner verified the match. But Spanish National Police examiners insisted the prints did not match Mayfield and eventually identified another man who matched the prints.
The FBI acknowledged the error and Mayfield was released.
Cole thinks the high-profile cases are the tip of an iceberg of wrongfully accused, cases that are sometimes swept under the rug or lead to convictions. Other studies have shown an error rate of 0.8 percent in matching prints. Multiplied across all cases processed by U.S. crime labs in 2002, that would b e 1,900 mistaken fingerprint matches.