A friend of Levy Rouse, whom prosecutors have portrayed as the ringleader in the fatal beating of Catherine L. Fuller, came under a scathing attack yesterday from prosecutors who attempted to show that he had lied when he testfied that Rouse was not in the alley when Fuller was killed and that, in fact, he also was in the alley and watched as Fuller was beaten to death.

Christopher D. Taylor, 16, of 1430 F Street NE, told a D.C. Superior Court jury that he and the 20-year-old Rouse spent Oct. 1, 1984, the day Fuller was killed, roaming the neighborhood, going to arcades, carryouts and parks. They ended up at the alley outside an abandoned garage where Fuller's battered body was found only after they saw parked police cars and were told that a girl had been killed, Taylor testified.

Taylor's testimony crumbled under a searing cross-examination by Assistant U.S. Attorney Jerry S. Goren. Taylor, who has not been charged in the case, was advised by Judge Robert M. Scott "to talk to your lawyer tonight" before testifying again today.

"Mr. Taylor, isn't it true you know what happened in that alley . . . because you were in that alley?" shouted Goren as he proceeded to fire off a series of questions about what Taylor allegedly told police about Fuller's death in several interviews.

Goren, reading from what appeared to be notes, asked Taylor if he told police that on Oct. 1, 1984, he heard a number of young people at a park talking about "getting paid" and then saw the group, which included Rouse, cross the street to follow a woman.

"Do you remember saying she was short and skinny and wearing a coat and carrying an umbrella . . . ?" Goren demanded. Prosecution witnesses have testified that Fuller, who was 4'11'' and weighed 99 pounds, was wearing a raincoat and carrying an umbrella the day she was killed.

"No," Taylor answered to each query, but as the pace of the questioning quickened, his answers became almost inaudible in the packed courtroom. Taylor, his voice shaking, acknowledged talking to police, but denied telling them anything about an assault in the alley.

Before Taylor took the stand on behalf of Rouse, who prosecutors charge is the man who rammed a foot-long pole into Fuller's rectum, defense lawyers argued out of the jury's presence over what Taylor would be permitted to testify about. Goren told Judge Scott that Taylor at various times had placed in the alley a number of the 10 defendants in addition to himself. As a result of those earlier admissions, Goren said he told police to read Taylor his rights and had a lawyer appointed for him.

Goren told the judge that Taylor had changed his stories several times, but that one prosecution eyewitness already had testified that Taylor was in the alley during the beating.

At one point, Judge Scott advised Taylor's lawyer, Ronald Goodbread, to again talk to his client and make certain Taylor understood he did not have to testify and that he could incriminate himself in such a way that might lead to prosecution. Moments later, Goodbread returned and said Taylor wanted to testify.

Taylor seemed at ease as he described to Rouse's lawyer, Lillian McEwen, how the two friends spent the afternoon. But that composure swiftly broke a few minutes later as Goren quizzed Taylor about discrepancies in his time sequence. At one point, Taylor told Goren he spent 1 1/2 hours at a carryout restaurant and then half an hour at a recreational center. Later, he reversed those times and then moments later again gave another set of times.

Goren then asked Taylor if he remembered what he was wearing Oct. 1, 1984. Taylor said he was wearing jeans, with a blue "gator" shirt and Nike tennis shoes. But asked what he was wearing the following day, Taylor said he could not remember. Taylor's clothing yesterday included jeans, a blue T-shirt with an alligator applique, and tennis shoes.

Earlier yesterday, the grandmother of one of the defendants, Edna Adams, said she knew her grandson Russell L. Overton, 26, also known as "Bobo," was not in the alley at the time Fuller was killed -- between 4:30 p.m. and 6:30 p.m. -- because she remembered he came home drunk about 3 p.m. and got into bed with his shoes on. He did not rise until about 7:30, she said.

"I took that stick and hit him across the legs," said the 72-year-old Adams, who along with her grandson lived on Ninth Street NE, only a few houses from the alley where Fuller was beaten. "I said, 'Get up. This is not a shanty place where tramps come in and lay.' "

Adams testified that another defendant, Timothy Catlett, 20, her sister's foster child since he was 2, also lived with her and Overton, but that he was not in the house that afternoon. Adams said that soon after Catlett, also known as "Snot Rag," returned to their home a young neighbor told her someone had been attacked in the alley.

Adams often seemed confused and gave conflicting testimony under cross-examination by Assistant U.S. Attorney Jeffrey Behm. She told the jury, "I'm 72 years old and I can't remember so much."

Also testifying yesterday was Mary Phyllis Overton, Russell Overton's sister. Under Behm's questioning, Overton said she had not spoken to her brother in jail about trying to find witnesses to present an alibi defense.

She said Overton told her, "If he was involved that he would have already had an alibi . . . and that he now would have things in order."

"And now he has an alibi," retorted Behm.