SOMERVILLE, N.J. — A key prosecution witness at Jayson Williams' manslaughter trial wavered Wednesday on whether the former NBA star played a big league role in covering-up the shooting of a chauffeur or only watched from the sidelines.

Williams' friend John Gordnick, who admits hiding the hoopster's Armani suit, size 15 shoes and other garments from police after the driver's death, insisted under cross-examination that the All-Star never directly told him to lie or destroy evidence.

"I just reacted, you know, saw a friend in trouble and just reacted," Gordnick said of his decision to hide Williams' garments in his car and later stash them on a highway overpass.

A short time later, however, when pressed by a prosecutor, Gordnick acknowledged that it was Williams who proposed the idea that driver Costas "Gus" Christofi killed himself Feb. 14, 2002, and that it was the defendant who later told witnesses in his mansion to fall in line with the phony account.

"I heard him to say out loud, 'Just stick to the story, just stick to the story,'" Gordnick said.

The 46-year-old personal trainer's testimony was filled with flip-flops and contradictions that perhaps indicated a desire to stay in the good graces of both his friend Williams and prosecutor Steven Lember.

Under a plea deal with Lember, Gordnick pleaded guilty to evidence tampering and agreed to take the stand against Williams. In exchange, the prosecutor dropped more serious charges.

Jurors had already heard some damaging testimony from Gordnick Tuesday. He recalled Williams wiped the shotgun that killed the 55-year-old driver free of prints and striped, washed himself and shoved a pile of clothes at Gordnick, saying, "Here J.G."

But when a lawyer for Williams cross-examined him Wednesday, he appeared to be an asset for the defense. During the friendly questioning, he implied it was another man, and not Williams, who took the lead in portraying Christofi's death as a suicide.

Gordnick said, that when it became clear to him that the cover-up had a "zero chance" of success, he pinned Williams' friend, Kent Culuko, against a wall, smacked him across the face and told him, "You got a better chance of hitting the lottery 365 days a year."

Jayson Williams listens to John Gordnick's cross-examination Wednesday.

When defense lawyer Billy Martin suggested Gordnick struck Culuko instead of Williams because "Kent had the appearance of being in charge and you knew he wouldn't get away with it," Gordnick agreed.

Culuko, who also struck a plea deal with prosecutors, is expected to testify later in the trial.

Williams, 36, faces 55 years in prison if convicted of eight counts related to the shooting and the cover-up. If convicted of only the cover-up charges, he likely will not be sentenced to prison.

Although the cover-up charges have minimal consequences in terms of sentence, the issue of who masterminded the deception is important to the defense as they fend off the more serious manslaughter charge.

Williams' lawyers maintain the shooting was an accident so tragic and unforeseeable that it left him stunned. Evidence that he immediately began organizing a large cover-up instead of seeking help for the dying man could undercut that assertion while testimony that he simply followed others while in a state of shock and panic could help him.

Since the trial began, four houseguests and a series of police officers have offered accounts of Williams' demeanor. Two troopers who took the stand after Gordnick said they overheard him tell a dining room full of witnesses not to give statements to police until his attorney arrived.

"He stood up and kinda gave an order. It was loud enough to carry throughout the room and out into the foyer," said Trooper Nicholas Giarnieri.

Prosecutors contend Williams was acting recklessly at the time of the shooting. They allege he was drunk and targeting Christofi, who had never worked for Williams before, for special abuse.

But Gordnick told jurors Williams did not seem intoxicated to him and was just joking with Christofi. He said, when the driver misunderstood a comment and began to leave, Williams ran after him, "put his arm around him, hugged him and brought him back in."

When initially questioned by prosecutors, Gordnick said he witnessed Williams, who had been drinking wine, sambuca and by some one account Scotch, drive his brand new Bentley fast and in a "very erratic" manner about a half hour before the shooting.

But after prosecutors showed him a video of the winding country road with a 50 m.p.h. speed limited the two had traveled, Gordnick said he had changed his assessment of Williams driving and no longer believed he was speeding.

Later, Lember showed him a statement in which he told police the Bentley had crossed the road's yellow line several times. The witness then retracted his retraction, saying Williams was driving "erratically," but adding that he would not call it "very erratically."

Throughout his time on the stands, Gordnick took pains to portray his friend in a positive light.

When Martin asked if Williams had been a gentleman at a Harlem Globetrotters game before the shooting, Gordnick quickly replied, "A complete gentleman."

When the lawyer asked if Williams "opened his home up to you with a lot of love?" Gordnick answered, "Absolutely."

In contrast, Gordnick appeared to be seething with bitterness as he recounted what he considered unfair treatment by prosecutors seeking his cooperation. He said authorities interviewed his children at their schools without his permission, called him an "unfit father" and a "scumbag" and got angry when he would not say what they wanted him to.

Later, however, after being pressed further by Lember about the treatment, he agreed that it was proper given the circumstances.

"They had a job to do. They had to kick some ass a little," said Gordnick. Williams, leaning forward on his elbows at the defense table, scowled at Gordnick throughout his testimony.

The trial will recess until Monday because of witness scheduling.