They forgot the gun. They forgot the gunfire. They forgot the defendant claiming he'd just shot a state trooper.

On the stand, a witness named Tamara Miller, testified that the events surrounding the Dec. 12, 2005, killing of a state trooper were "all a blur."

But in taped police interviews in the days after Cpl. Joseph R. Pokorny was slain, she and four key prosecution witnesses gave detailed accounts of defendant Leslie D. Mollett's involvement in the crime.

The jury has heard the same thing over and over during the trial in Allegheny County Common Pleas Court, now heading into its fourth week: A witness who remembers almost nothing on the stand is heard recalling many details on taped interviews made around the time of the homicide.

Police investigators and prosecutors are familiar with the way that details evaporate -- whether it's due to the effect of time on memory, the presence of those pressuring the witness to forget or antagonism toward the judicial system. That's why a tape recording is often a prosecutor's best friend.

Butler County District Attorney Randa Clark -- who has no involvement with the Mollett case -- said that while taped statements can present difficulties in trial when witnesses don't say the same thing on the stand, they are often invaluable to prosecutors.

"It stands to reason that people's memory is diminished in time. As more and more time elapses, so does one's recollection," said Ms. Clark, who became a prosecutor in the district attorney's office in 1991 and has been district attorney since January 2006.

Witnesses who give statements right after an event often become hostile witnesses over the course of time, she said.

"It happens all the time," she said. "By the time the case comes to trial your victim is in the process of recanting, trying to deny that statements they made were true at time they made them."

In the case of the Mollett trial, witnesses have presented themselves largely as forgetful, rather than hostile.

Tamara Miller, the mother of the defendant's two daughters, testified on the stand, "I don't recall ... This is all a blur, it really is."

But on tape Dec. 12, 2005, Ms. Miller said, "Nobody but me and him knew where the gun was."

Ms. Miller said she and Mr. Mollett were together for about 10 years. She is the registered owner of a Glock semiautomatic recovered at the scene. The gun had DNA on it matching Mr. Mollett's profile, according to an expert from the state police crime lab. When police came to her home, she told them the gun was there, but when she went to retrieve it, it was gone. Ms. Miller said on tape that only she and Mr. Mollett knew where it was and that "my kids never knew."

Phillip Peterson, a friend of Mr. Mollett for 20 years, testified on the stand, "Uh, no. I don't know if it was a gunshot but I didn't hear no gun being fired."

But on tape Dec. 13, 2005, he said, "I heard like three or four shots. TUK-TUK-TUK. TUK-TUK-TUK."

Under questioning from Deputy District Attorney Mark V. Tranquilli, he said he didn't remember seeing Mr. Mollett jostling in the car in which they were riding to hide his weapon, didn't remember hearing gunfire as he ran from the scene, did not remember that later that day he got a cell phone call from Mr. Mollett who said "He's hit. Three to the head." He also didn't remember a second call from the defendant asking him to go back to the scene and recover his Glock.

On a second day in court, after being ruled a hostile witness, he said, "I can't remember," "I don't remember saying that," "I didn't say that" and "I'm sticking to my story," repeatedly.

Jabbar "Bar" O. James, who has been friends with Mr. Mollet for more than 20 years, testified on the stand, "I don't recall," when asked by Mr. Tranquilli if he heard anything as he and Mr. Peterson fled over a hillside.

But on tape Dec. 13, 2005, he said, "As we were going over the cliff, I hear three to four shots." He described the sound as: "P-pow-pow."

He also testified that he didn't recall seeing Mr. Mollett handling the gun in the car, didn't recall the details of the exchange with Cpl. Pokorny, didn't remember whether Mr. Mollett changed into different clothing following the traffic stop and didn't remember saying that he was eager to see the videotape from the trooper's patrol car because it would clear him of the killing.

Jamekia D. Robinson, mother of Phillip Peterson's 11-year-old daughter, testified repeatedly on the stand, "Not that I recall."

But on tape Dec. 14, 2005, describing the gathering of Mr. Mollet and the group he had gone out with that night at her house after the traffic stop, she said, "A couple of them asked Les, 'The cop tried to handcuff you, why didn't you just let him?' "

She said that when they heard on TV that a state trooper had been shot, some of the men asked if Mr. Mollett had shot him. He did not answer, Ms. Robinson said. When the update came on saying that Cpl. Pokorny was dead, Mr. Mollett left and most of the other guys left.

Andrew "Heater" Palmer, a member of the group out with Mr. Mollett, said in court more than 30 times that he did not recall the events of Dec. 12.

Yet on tape Dec. 22, 2005, Mr. Palmer recalled that at Ms. Robinson's place after the traffic stop, Mr. Mollett said that he had grabbed the trooper's gun and fired it. He said Mr. Mollett said he thought he might have shot the trooper in the head because he saw blood gushing from his nose.

Mr. Palmer, whose attorney sought to keep him from being forced to testify, said he didn't remember so many times that when Mr. Tranquilli asked if he remembered making a statement to police on Dec. 22, 2005, Common Pleas Judge Lawrence J. O'Toole interrupted, saying "I take it you don't remember."

"I don't recall," Mr. Palmer responded.

In the course of the Mollett trial, defense attorney John Elash has repeatedly poked at the changes in witnesses' stories.

Any time a witness's version of events varies, it's always a target for the opposing attorney to use to point out inconsistencies, Ms. Clark said.

The passage of time does make memory loss understandable, said Stanton Levenson, a criminal defense attorney. Sometimes years pass between the crime and the trial.

In addition, testifying is very different from giving a statement.

"The dynamics are different," he said. "When you're giving a statement, you're giving it to police. The defendant is not there. The lawyer is not there. There's no prospect of cross-examination, which can be very unpleasant."

Still, the recorded statements often have the ring of truth.

"There is an element of truth that doesn't exist later on," Ms. Clark said. "There's less time for cool reflection, less time to corrupt what the original statement was. There are a multitude of reasons [for people to change their stories and] contacts that take place, particularly if they are close to the person on trial."

With a taped statement, "the advantage clearly goes to prosecution," said Mr. Levenson.

"It's much more difficult for defense lawyers," he said. "It's very difficult for a witness to credibly claim at a later date that they didn't mean what they said."