On 6 May 2004, a Portland, OR, lawyer named Brandon Mayfield was arrested for his alleged involvement in the terrorist bombings of four commuter trains in Madrid, Spain. The sole evidence against him was a partial fingerprint found on a plastic bag. The FBI's Integrated Automated Fingerprint Identification System had identified Mayfield as a possible match, and three FBI fingerprint experts as well as an outside expert confirmed the identification. Spanish authorities, however, strenuously argued that the fingerprint belonged not to Mayfield but to an Algerian with a criminal record, Spanish residency, and known terrorist links.
The Spanish authorities were right. The U.S. government eventually agreed to pay Mayfield U.S. $2 million for the mistake and issued a formal apology.
This is only one of countless examples of forensic analysis gone wrong. And yet, such traditional forms of forensic evidence can be very helpful, provided they are examined objectively and that the uncertainty of the results can be measured and properly explained. This is where computers have a role to play. The relatively new field of computational forensics has sprung up to address this.
Computational forensics is not yet mainstream, but much research goes on in academic settings, and eventually the courts may allow these techniques to be applied in actual criminal trials.
The issue is explored in "Computing the Scene of a Crime" by Sargur N. Srihari, published in the December 2010 issue of IEEE Spectrum.