§ 24.10 FINGERPRINT EVIDENCE

• Jurisdiction: United States

§ 24.10. FINGERPRINT EVIDENCE

In United States v. Llera Plaza,¹⁸⁴ the trial judge held that a fingerprint expert could not give an opinion that two sets of prints "matched" — that is, a positive identification. And then, he reversed himself after an evidentiary hearing.¹⁸⁵ The prosecution had argued that latent fingerprint identification had been "tested" for nearly 100 years in adversarial proceedings with the highest possible stakes. However, Llera Plaza I pointed out that Daubert requires scientific, not judicial, testing:

"[A]dversarial" testing in court is not, however, what the Supreme Court meant when it discussed testing as an admissibility factor. . . . It makes sense to rely on scientific testing, rather than "adversarial" courtroom testing, because to rely on the latter would be to vitiate the gatekeeping role of federal trial judges, thereby undermining the essence of Rule 702 as interpreted by the Court in Daubert. . . . Thus, even 100 years of "adversarial" testing in court cannot substitute for scientific testing when the proposed expert testimony is presented as scientific in nature.

In Llera Plaza II, the prosecution offered evidence of the FBI's proficiency testing. There was one "false positive" in sixteen external tests taken by supervisory examiners. In addition, the

internal tests taken over the seven years numbered 431. These tests generated three errors, two in 1995 and one in 2000. Each of the three errors was a missed identification — i.e., a failure by the test taker to find a match between a latent print and a known exemplar which in fact existed; such an error is a "false negative" which, being mistakenly exculpatory, is regarded by the FBI as considerably less serious than a false positive. In sum, the 447 proficiency tests administered in the seven years from 1995 through 2001 yielded four errors — a proficiency error rate of just under 1%.¹⁸⁶

Nevertheless, defense experts were highly critical of the way in which the tests were conducted. A fingerprint examiner, who had worked for 25 years at New Scotland Yard, testified that the FBI tests were too easy: "It's not testing their ability. It doesn't test their expertise. I mean I've set these tests to trainees and advanced technicians. And if I gave my experts these tests, they'd fall about laughing."¹⁸⁷ Two other defense experts were not fingerprint examiners but experts on testing (psychometrics). Both were critical of the FBI proficiency tests: "The test materials and...