1. Although Mayfield and Daoud did not have identical fingerprints, they did, nevertheless, have very similar-looking prints;
2. After the FBI found as many as 10 points of unusual similarity between Mayfield’s fingerprint and the fingerprint located on the bag of detonators, "the FBI examiners began to ‘find‘ additional features in [the fingerprint on the bag] that were not really there, but rather were suggested to the examiners by features in the Mayfield prints. As a result of this process, murky or ambiguous details in [the fingerprint on the bag] were erroneously identified as points of similarity with Mayfield’s prints."
3. The FBI fingerprint examiners "apparently misinterpreted distortions in [the fingerprint on the bag] as real features corresponding to [extremely tiny details] seen in Mayfield’s known fingerprints." Thus, whereas error #1 had to do with comparatively large fingerprint details, error #3 had to do with extremely tiny details.
4. FBI fingerprint examiners are taught to adhere to the "one discrepancy rule" according to which "a single difference in appearance between [an unknown] print and a known fingerprint must preclude an identification unless the examiner has a valid explanation for the difference." In Mayfield’s case, the examiners failed to adhere to this rule when they accepted an "extraordinary set of coincidences" and "cumulatively required too many rationalizations to support an identification with the requisite certainty."
5. As noted in error #2 above, the FBI found as many as 10 points of unusual similarity between Mayfield’s fingerprint and the fingerprint located on the bag of detonators. "However, the limited clarity of [the fingerprint on the bag] prevented the examiners from making an accurate determination of the type of many of these points (that is, whether they were ending ridges or bifurcations)."
6. Although the Spanish National Police advised the FBI on April 13, 2004 that the fingerprint on the bag of detonators did not match Mayfield’s prints, the FBI nevertheless arrested Mayfield more than three weeks later on May 6, 2004. In what is certainly an understatement, the OIG concluded that "the FBI Laboratory’s overconfidence in the skill and superiority of its examiners prevented it from taking the [April 13 report] as seriously as it should have." According to the OIG, what the FBI should have done was:
Determine precisely why the Spanish National Police examiners believed that Mayfield’s fingerprints did not match the print on the bag before arresting him; and
Have a new FBI examiner examine the fingerprint on the bag in order to verify whether or not it was Mayfield’s.
In reviewing the OIG’s report, the two things that stand out to me the most are:
The fact that the six errors discussed in this article were committed by not just one person but by four people including: a fingerprint examiner with the FBI Latent Print Unit, a second FBI Latent Print Unit examiner, a Unit Chief in the FBI Latent Print Unit, and an independent expert appointed by the judge to review the FBI’s fingerprint identification.
The fact that the FBI arrested Mayfield, searched his home and office, and took items from those two locations three weeksafter being told by the Spanish National Police that Mayfield’s fingerprints did not match the print on the bag of detonators.
Ronald S. Chapman, P.A.
400 Clematis Street, Suite 206 West Palm Beach, FL 33401
Tel: (561) 832-4348 | Fax: (561) 832-4346
If you have been charged with a crime or would like to get your record sealed in West Palm Beach, Palm Beach, Belle Glade, Boynton Beach, Delray Beach, Jupiter, Lake Park, Lake Worth, Lantana, North Palm Beach, Palm Beach Gardens, Palm Springs, Riviera Beach, Royal Palm Beach, or Wellington, call me, Attorney Ron Chapman, at 561-832-4348 to discuss your case and see how I might be able to help you.