SJC bars a type of prints at trial

In a rare setback for fingerprint evidence, the state's highest court yesterday barred prosecutors from presenting evidence that prints found on the vehicle of a slain Boston police detective came from a suspect who allegedly touched a window with several fingertips at once.

The ruling by the Supreme Judicial Court in the case of Terry L. Patterson, a former Dorchester man accused of murdering John J. Mulligan in 1993, affects only the sliver of cases in which fingerprint examiners add up characteristics from several prints to look for a match, about 1 percent of all cases involving prints, according to a prosecutor.

The ruling does, however, represent a significant victory for Patterson. The 17-page decision quashes the only physical evidence tying him to the slaying, although both prosecutors and Patterson's own lawyer expected the case will still go to trial.

Overall, the high court upheld fingerprints as reliable evidence, disappointing critics of the century-old forensic science who have argued more frequently in recent years that it is not really a science, in hope of having it barred from criminal trials.

''It's a little chink in fingerprints' armor," said Simon A. Cole, an assistant professor of criminology at the University of California at Irvine who signed a friend-of-the-court brief urging the court to reject fingerprint analysis until it is proven reliable through rigorous scientific scrutiny. ''It would have taken a great deal of courage [to reject all fingerprint evidence], but we hoped that we had a court that had that courage."

Cole said he was aware of only one other instance in which a US court has rejected fingerprint evidence as unreliable.

In January 2002, he said, US District Judge Louis H. Pollak of Philadelphia stunned the legal community when he said fingerprint evidence does not meet accepted standards of scientific scrutiny and barred fingerprint examiners from testifying. Pollak reversed himself two months later.

Suffolk District Attorney Daniel F. Conley, who enlisted prosecutors across the state to submit briefs supporting fingerprint identification, said he was pleased that the court upheld such evidence for most criminal trials.

''The Supreme Judicial Court's decision underscores what a century of investigations and prosecutions have established: Fingerprint evidence is a valid and credible science based upon clear, definable standards of analysis and verification," said a statement Conley released.

He said prosecutors were reviewing whether they can revive the quashed evidence in the Patterson case by addressing shortcomings cited by the court. Those weaknesses include an apparent lack of acceptance by professional fingerprint examiners of prints like those allegedly left by Patterson.

''We continue to prepare to retry Terry Patterson and are confident he will again be held accountable for the tragic murder of Boston police Detective John Mulligan," Conley said.

Patterson and a friend, Sean K. Ellis, were convicted at separate murder trials in the Sept. 26, 1993, slaying of Mulligan, who was shot five times in the face as he sat in his Ford Explorer in a Roslindale parking lot.

But the SJC overturned Patterson's conviction in 2000, ruling that his lawyer should have removed herself from the case and testified as a defense witness when it became clear she had information that disputed police testimony.

As the state prepared to retry Patterson, his lawyer, John H. Cunha Jr., sought to quash pivotal fingerprint evidence presented at the first trial.

Boston police Sergeant Robert Foilb had testified that three latent prints recovered on the driver's side window of the Explorer belonged to Patterson. He reached that conclusion by adding up so-called ''ridge characteristics" from three fingers -- six on one, two on another, and five on the third -- a method Cunha later called ''crazy."

Cunha contended that Foilb added up the matching characteristics because there were not enough points of similarity on each fingertip.

Detractors of fingerprint analysis say that the number of points needed to make a match varies from police department to police department, giving rise to what David M. Siegel, a New England School of Law professor, called a ''knows it when he sees it" approach for fingerprint analysts. Siegel helped write the friend-of-the-court brief on behalf of a group of scientists and scholars that included Cole.

But Cunha went beyond the Patterson case, saying that fingerprint analysis was, as he put it in a September interview with the Globe, ''a house of cards" that had never been systematically studied for reliability.

He cited recent high-profile misidentifications, including last year's exoneration of Stephan Cowans of Roxbury, who was convicted of the 1997 gunshot wounding of a Boston police sergeant after a thumbprint on a glass mug found near the crime scene was misidentified as his.

But Suffolk prosecutors countered that fingerprint analysis withstands scrutiny every day in criminal cases.

Mistakes are infinitesimal and always the result of human errors, prosecutors said, making fingerprint analysis one of the most reliable crime-fighting tools.

In the end, the high court upheld most fingerprint evidence as valid, citing widespread support by a ''sufficiently broad community of technical experts." However, the court said that matching several prints to a suspect's fingertips when no individual prints can be declared a match lacks such widespread acceptance.

Robert C. Cosgrove, an assistant Norfolk district attorney who submitted a friend-of-the-court brief on behalf of state prosecutors, said the court left the door open for Suffolk to prove that the use of fingerprints like those prosecutors sought to introduce in Patterson's case does pass muster with fingerprint analysts.

Jonathan Saltzman can be reached at jsaltzman@globe.com.