The sanctity of the oath taken by a witness is the most essential bulwark of the truth-seeking function of a trial, which is the American method of ascertaining the facts.

"It's a long-overdue reform that hopefully will help the truth-seeking function in police investigations," said a senior federal prosecutor who has handled a number of police corruption cases and would speak only on condition of anonymity.

Of the guilty pleas, he said: "Perjury is a very serious crime that jeopardizes the truth-seeking function of the grand jury.

Rather than work with the judicial and legislative branches to uphold the rule of law, he directly attacked their fundamental truth-seeking function.

We must neither reward nor condone such a 'flagrant affront' to the truth-seeking function of adversary proceedings. . . . Perjury should be severely sanctioned in appropriate cases.

But the court said in its 3-to-2 decision, "We believe that the truth-seeking function is best served by keeping the door open to scientific advances."

This suggestion has no basis in law, and it is destructive to the truth-seeking function of the courts.

"When a defendant becomes a witness, he has no constitutional right to consult with his lawyer while he is testifying," he said, describing the rule as among those "that serve the truth-seeking function of the trial."

"That is my position," Mr. Dreeben said, adding, "There is a terrible cost to the truth-seeking function of a criminal trial to suppress reliable physical evidence" simply because the statement leading to its discovery was "unwarned."

In dissent, Justice Anthony Kennedy objected to what he called the impairment of "the truth-seeking function of a criminal trial."