A Harder Day in Court for Fingerprint, Writing Experts ; US Judge Limits Testimony of Forensic Analysts, in a Ruling That Might Alter How Evidence Is Presented at Trial

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For decades, fingerprinting and handwriting analysis have enjoyed sure acceptance in American courts.

But now, in an age of scientifically grounded DNA analysis, judges are looking with increased skepticism at forensic techniques that rely solely on the subjective experience of experts.

Last week, Philadelphia federal judge Louis Pollak ruled a fingerprint expert could not testify that a suspect's prints definitively matched those found at a crime scene. Other courts have also recently knocked out testimony from handwriting and knife-mark experts.

Legal observers view the decision by Judge Pollak as a breakthrough that could lead to major changes in the way everything from firearms to bite marks are investigated and presented in court.

"Courts are forcing forensic science to become a science - to actually test its claims, determine its error rates, and not overstate conclusions," says Michael Saks, a law professor at Arizona State University in Tempe.

Both fingerprinting and handwriting analysis were developed by police in the early 1900s, based on the premise that each person's unique prints or penmanship assures that the right suspects are tied to their crimes.

But fingerprint experts and their critics have disagreed over how well a partial print lifted from a crime scene can be matched with certainty to a full print culled from a database.

Still, until a decade ago, federal judges were limited in their discretion to bar an expert's testimony. To make such a determination, the judges could only ask whether the testimony was accepted within the community of experts in that field.

But then, in 1993, the Supreme Court gave federal judges the power to decide for themselves whether an expert's testimony was sufficiently grounded in science to be admitted. In effect, this made federal judges the gatekeepers over all scientific and forensic evidence.

In recent years, defense attorneys have launched at least a dozen challenges to fingerprinting analysis. Before last week, though, none had succeeded.

In his decision, however, Judge Pollak found that although fingerprint science had been accepted in court for 90 years, it hadn't been proved scientifically. …