The report found " FBI fingerprint examiners relied in significant part on the relationship of "minutiae" or "points" within the prints. These points are places where individual ridges in the fingerprint end or split (ending ridges or bifurcations). These 10 features in Latent Finger Print 17 formed a constellation of points that was generally consistent with the constellation of points in the known fingerprints of both Mayfield and Daoud. The unusual similarity is reflected in the relative location of the points, the orientation of the ridges coming into the points, and the number of intervening ridges between the points. Although the OIG found no systematic study of the rarity of such an event, anecdotal reports suggest that this degree of similarity between prints from two different people is an extremely unusual circumstance."
As every latent fingerprint examiner knows, the minutiae/points is the level II detail. In the 70's as a latent fingerprint examiner, my agency required a minimum number of minutiae or points before a latent fingerprint examiner was allowed to testify in court to an identification. Many other agencies had similar policies. The question that this case brings up is what is the reliability of an identification with 10 or fewer minutiae or points ? I realize a lot has to do with the clarity and uniqueness of the minutiae, but when you're dealing with 10 or fewer points they are usually poor/marginal quality images.
The bias from the examplar tenprint card. " The OIG found that a significant cause of the misidentification was that the Latent Print Unit fingerprint examiners' interpretation of some features in Latent Finger Print 17 was adjusted or influenced by reasoning "backward" from features that were visible in the known fingerprints of Mayfield. This bias is sometimes referred to as "circular reasoning," and is an important pitfall to be avoided. Having found as many as 10 points of unusual similarity, the FBI fingerprint examiners began to "find" additional features in Latent Finger Print 17 that were not really there, but rather were suggested to the latent fingerprint examiners by features in the Mayfield prints. As a result of this process, murky or ambiguous details in Latent Finger Print 17 were erroneously identified as points of similarity with Mayfield's prints."
I'd like to think an experienced latent fingerprint examiner would not allow this bias to influence a decision, but even 4 experienced latent fingerprint examiners were influenced into a bad identification. The most effective way to guard against this would be to have an unbiased 3rd. party latent fingerprint examiner analyze the fingerprint without any knowledge of previous determinations.
Level III detail, "The OIG also found that the FBI latent fingerprint examiners gave significant weight to the purported agreement between extremely tiny details in Latent Finger Print 17 and Mayfield's fingerprints. These details, including shapes interpreted as individual pores, incipient dots between ridges, and ridge edges, are known as "Level 3" details. Because Level 3 details are so small, the appearance of such details in fingerprints is highly variable, even between different fingerprints made by the same finger. As a result, the reliability of Level 3 details is the subject of some controversy within the latent fingerprint community. The OIG found that none of the purported Level 3 features in Latent Finger Print 17 used to identify Mayfield corresponded to features in the known fingerprints of the true donor (Daoud). Thus, unlike the case with larger details, the examiners were not confused by any unusual similarity in Level 3 details on the fingerprints of Mayfield and Daoud. Rather, they apparently misinterpreted distortions in Latent Finger Print 17 as real features corresponding to Level 3 details seen in Mayfield's known fingerprints."
As a latent fingerprint examiner, I rely on Level II detail to make my determination of identification, I do use some Level III detail (ridge shape, etc.) in conjunction with the Level II (ending ridges, bifurcations, etc.) detail, during my comparison and evaluation of the prints. I have not had a situation where my determination of identification relied solely on Level III detail.
One discrepancy rule is followed by all latent examiners, if there is an unexplainable difference in the latent and tenprint fingerprint card, it must be declared a non-identification. "The FBI recognized that the entire upper left portion of Latent Finger Print 17 did not correspond with Mayfield's fingerprint. The examiners explained this difference as being the result of a separate touch, possibly by a different finger or a different person. This explanation required the examiners to accept an extraordinary set of coincidences. The OIG found that the support for this explanation was, at best, contradictory fingerprint examiners are governed by the "one discrepancy rule" in which a single difference in appearance between a latent print fingerprint and a known fingerprint must preclude an identification unless the examiner has a valid explanation for the difference. Latent fingerprint identifications are subject to a standard of 100 percent certainty. Implicit in this standard is the requirement that the examiner have equivalent certainty in the validity of each explanation for each difference in appearance between prints."
"The OIG also found that the FBI examiners failed to give adequate consideration to the incomplete nature of the agreement in points between Latent Finger Print 17 and Mayfield's fingerprint. As previously described, there was a constellation of as many as 10 points in LFP 17 that bore an unusual similarity to points in the Mayfield fingerprint. However, the limited clarity of Latent Finger Print 17 prevented, the latent fingerprint examiners from making an accurate determination of the type of many of these points (that is, whether they were ending ridges or bifurcations). The OIG found that many of the points utilized by the FBI to support the identification suffered from this shortcoming (ambiguity as to feature type), and that accordingly the "quality" of the agreement was inadequate to support the conclusion of identification." Apparently the latent fingerprint examiners allowed themselves to be influenced by each other and the tenprint fingerprint card.
What is clear from the Madrid bombing error is that even highly trained and experienced latent fingerprint examiners can make identification errors. Most latent fingerprint examiners testifying in court today, don't have near the training or experience of the 4 individuals above and often the identification is based on the opinion of only 1 latent fingerprint examiner. The automated fingerprint identification systems today are designed to find candidate fingerprints having the most minutiae arrangements similar to the encoded minutiae from the latent fingerprint. These candidates should include the correct match of the print (if it is in the database), but will also include the closest possible non-matches. These close non-match suspects require more fingerprint comparison experience than many of today's latent examiners have been able to acquire.
Bob McAuley
Dir. Operations/Training
Forensic Biometric Identification Solutions LLC.
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