March 9, 2002

Will Fingerprinting Stand Up in Court?


In 1993, when the Supreme Court demanded real scientific standards for expert evidence in federal courts, some critics correctly anticipated that several criminal identification techniques would be attacked in the courts with some success: microscopic hair comparison, bite mark analysis, handwriting comparison. Few, if any, predicted what is happening now: The bedrock forensic identifier of the 20th century, fingerprinting, has started to wobble.

In a pretrial hearing in a Philadelphia federal court in January, Judge Louis H. Pollak sharply limited the use of fingerprint evidence in a drug-related murder case. He found that there is no persuasive proof that the methods used by fingerprint analysts have been adequately tested in objective, controlled experiments.

The problem is that though fingerprints do seem to be unique identifiers, any print must be read and matched. The question one that can only be answered by rigorous scientific inquiry is how much of a match is required to say that a particular fingerprint is from a particular person.

Fingerprint experts had conceded that the process they use matching large, evenly pressured prints taken from suspects at the police station to smaller, unevenly pressured prints from crime scenes is ultimately subjective and bedeviled by inconsistent standards. The French, for example, require that two fingerprints match at 16 points before they can be accepted as coming from the same person; the Australians, 12; and the Swedes, 7. The F.B.I. refuses to state a number at all, relying instead on case- by-case judgments.

Judge Pollak, who is a former dean of the law schools at Yale and the University of Pennsylvania, also noted "alarmingly high" error rates when fingerprint examiners took proficiency tests; in 1995 only 44 percent of 156 law enforcement examiners could correctly identify all five prints in the test, and in a 1998 study the number improved to only 58 percent.

In the coming murder trial, Judge Pollak ruled, fingerprint experts will not be allowed to express an opinion about whether fingerprints match, but will only be allowed to testify as to the points they see as similar.

As prosecutors quickly recognized, the judge's ruling calls into question the overall acceptance of fingerprint evidence in our courts. In a motion last month for reconsideration of the ruling, the United States attorney cautioned that the implications of the court's opinion "undermine not only the admission of fingerprint evidence . . . but all manner of forensic opinion testimony."

No one doubts that fingerprints can, and do, serve as a highly discriminating identifier, and digital photographic enhancement and computer databases now promise to make fingerprint identification more useful than ever before. But to what degree incomplete and imperfect fingerprints can be reliably used to identify individuals requires more scientific examination. And the criminal system needs forensic examiners who can pass rigorous proficiency tests.

Forensic science has rarely been subjected to the kind of scrutiny and independent verification applied to other fields of applied and medical science. Instead, analysts testifying in courts about fingerprint analysis, bite marks, handwriting comparisons and the like have often argued that in their field the courtroom itself provided the test. New York is the only state that regulates crime laboratories with standards even approaching those routinely used for clinical medicine.

As the National Institutes of Health finance basic scientific research, the National Institute of Justice should put money into verification and validation before a technique of identification is admitted in court. Academic centers should be established for research into these questions under the aegis of medical and law schools.

Independence and scientific rigor should be the norm for forensic science. Crime victims, the wrongly accused, and the public will all have more confidence in the system if forensic scientists and their laboratories are completely independent, not beholden to prosecutors or defense attorneys.

Peter Neufeld and Barry Scheck are directors of the Innocence Project at the Benjamin N. Cardozo School of Law at Yeshiva University.

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