Lie detectors could curb police perjury.

Los Angeles Police Department detective Mark Fuhrman's testimony in the O.J. Simpson trial under scores the seriousness of police perjury in the U.S. legal system, states Donald Dripps, a University of Illinois law professor. Although no one knows exactly how wide-spread the problem is, many experienced trial lawyers have said they believe police officers frequently lie on the stand. Preliminary studies appear to back up that belief.

The temptation to lie may be greatest during evidence-suppression hearings, which are heard by a judge rather than by a jury. Crucial evidence can be suppressed if a judge rules that an officer violated the Constitution by entering a residence without a search warrant or failing to obtain consent to search the trunk of a car, for example. "In your standard suppression situation, where the defendants are guilty criminals and the witness for the prosecution is a police officer, the deck is stacked," Dripps points out. Judges are far more likely to credit an officer's testimony, even if they're skeptical of it, over the testimony of a defendant caught with a suitcase full of drugs. "As you might expect in that situation, the police are tempted to lie because they know they can get away with it."

According to Dripps, the use of lie-detector testing in evidence-suppression hearings might make it more difficult for police officers to perjure themselves. Lie detectors would be used to help establish witness...