Box 1-1

FBI Statement on Brandon Mayfield Case

“After the March terrorist attacks on commuter trains in Madrid, digital images of partial latent finger prints obtained from plastic bags that contained detonator caps were submitted by Spanish authorities to the FBI for analysis. The submitted images were searched through the Integrated Automated Finger print Identification System (IAFIS). An IAFIS search compares an unknown print to a database of millions of known prints. The result of an IAFIS search produces a short list of potential matches. A trained finger print examiner then takes the short list of possible matches and performs an examination to determine whether the unknown print matches a known print in the database.

Using standard protocols and methodologies, FBI finger print examiners determined that the latent finger print was of value for identification purposes. This print was subsequently linked to Brandon Mayfield. That association was independently analyzed and the results were confirmed by an outside experienced finger print expert.

Soon after the submitted finger print was associated with Mr. Mayfield, Spanish authorities alerted the FBI to additional information that cast doubt on the findings. As a result, the FBI sent two finger print examiners to Madrid, who compared the image the FBI had been provided to the image the Spanish authorities had.

Upon review it was determined that the FBI identification was based on an image of substandard quality, which was particularly problematic because of the remarkable number of points of similarity between Mr. Mayfield’s prints and the print details in the images submitted to the FBI.”

The FBI’s Latent Finger print Unit has reviewed its practices and adopted new guidelines for all examiners receiving latent print images when the original evidence is not included.

SOURCE: FBI. May 24, 2004, Press Release. Available at

own review by a panel of independent experts. The reviews concluded that the problem was not the quality of the digital images reviewed, but rather the bias and “circular reasoning” of the FBI examiners.31

Parts of the forensic science community have resisted the implications of the mounting criticism of the reliability of forensic analyses by investigative units such as Inspector General reports, The Innocence Project,


U.S. Department of Justice, Office of the Inspector General. 2006. A Review of the FBI’s Handling of the Brandon Mayfield Case. Also see R.B. Stacey. 2005. Report on the Erroneous Fingerprint Individualization in the Madrid Train Bombing Case. Available at

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