A witness pleaded guilty yesterday to lying under oath in a D.C. murder trial that ended earlier this year with a hung jury.

Jermaine Davis, who was due to go on trial this week in D.C. Superior Court, pleaded guilty to perjury in exchange for a five-year prison sentence. The case is among a string involving perjury charges that have been brought this year by the U.S. attorney's office, which has taken a more aggressive approach to a problem that many prosecutors say has become pervasive.

Davis, 24, was expected to be a key prosecution witness in the trial last April of Adrian Wade. Wade, now 27, was accused of murder in the October 1999 killing of Ba Nin Le, a Vietnamese immigrant, in Southwest Washington. After the jury deadlocked, prosecutors retried the case -- this time, without Davis's testimony -- and Wade was acquitted of the murder charge.

Before taking the case against Wade to trial, prosecutors said they believed that Davis would testify that Wade had admitted the crime to him. That is what he told police detectives, as well as grand jury, according to prosecutors.

But when called to the witness stand April 5 at Wade's trial, Davis told a different story.

Under questioning by Assistant U.S. Attorney Steven B. Snyder, Davis said he had never talked to Wade about the killing. He said his earlier, contrary statements were the result of intimidation and manipulation by investigators.

"I told what they wanted me to say," he testified at the trial.

"So you lied under oath before the grand jury?" Snyder asked.

"I didn't lie. They forced me to lie. They wanted me to lie," Davis testified, referring to the police.

The U.S. attorney's office has charged at least six witnesses with perjury this year, almost as many as had been charged in the three previous years combined. Three cases, including Davis's, have led to convictions; the others are scheduled for trial this year or early next year.

Several defense attorneys who try cases in Superior Court have expressed concern about the spike in perjury charges. The threat of perjury charges can intimidate witnesses and lead them to make up stories to match what they believe police and prosecutors want to hear, the defense lawyers said.

Davis's guilty plea could be rescinded if Judge Gerald I. Fisher declines to go along with a five-year prison term. The judge set a Nov. 9 sentencing date.

Gary Sidell, Davis's attorney, said his client pleaded guilty because "he wants to get on with his life."

But he said that the prosecution of Davis for perjury was personal. Another prosecutor, David Saybolt, handled the perjury case, but Sidell said Snyder was the driving force behind it.

"He couldn't convict Wade," Sidell said, "so by God, he was going to make Davis pay for it."

During Wade's trial, Davis testified that police and prosecutors were pressuring him, especially after he told them that what he had said before the grand jury was not true. They offered to move him to North Carolina and to help him if he helped them, Davis told Wade's lawyer, Ronald Horton of the D.C. Public Defender Service.

"But if I don't help them, they can't give me no help," he testified. "I'll be on my own. Something might happen to me . . . or they're going to make sure I don't leave out of this courtroom unless I'm charged with perjury because I'm not going to help them out."

Snyder's questioning at the murder trial raised the prospect that Wade may have influenced Davis's decision to change his story.

"Isn't it true, Mr. Davis, that in the jail, you told us that Mr. Wade came up to you and asked you if you were a snitch, and then said if anyone asks you about this case, take the perjury charge, do the five to ten?" the prosecutor asked.

Davis denied making any such statement. "I don't remember saying nothing like that, sir," he said.