Levy Rouse, the man prosecutors say committed the most savage attack on Catherine L. Fuller, took the witness stand yesterday and testified that he arrived at the alley where Fuller's body was found only after a "little person wrapped in a sheet" was carried out on a stretcher.

Rouse, his voice quavering as he told a D.C. Superior Court jury his account of Oct. 1, 1984, testified that a police officer at the scene told him a "little girl was dead." The 20-year-old Rouse said he became upset, jumped around and asked who could do "all those terrible things."

Rouse's testimony, coupled with the account delivered Thursday by his main alibi witness, fueled an unusually bitter rift among defense lawyers, some of whom charged that Rouse's defense was so incredible that it would contaminate the defenses of the nine other persons on trial for the murder and robbery of the 48-year-old Northeast woman.

"Their Rouse's witnesses' credibility has been destroyed," defense lawyer Steven Kiersh insisted as he asked Judge Robert M. Scott out of the jury's presence for a separate trial for his client, Steven Webb, 20. The "prejudicial effect," Kiersh said, of being "associated or linked now with Levy Rouse on any day of any year is terribly, terribly damaging."

Earlier, after 16-year-old Christopher D. Taylor concluded his testimony that he and Rouse spent the afternoon of Oct. 1, 1984, visiting neighborhood arcades and carryouts, defense lawyer Allan Palmer blasted Rouse's defense as he asked for a separate trial for his 26-year-old client, Russell L. Overton.

"It's like pornography, it has not one whit of redeeming value," Palmer told Scott, again out of the jury's presence.

Scott tartly denied all severance motions, reminding the lawyers that their cases do not rest on Rouse's defense. To Kiersh, Scott said, "I'll tell you what has been devastating for your client . . . . It's the direct evidence that has been introduced against him." And to Palmer, Scott questioned the accuracy of an alibi witness Palmer called to the stand Thursday, Overton's 72-year-old grandmother.

"This lady didn't know what she was talking about," Scott said. Then he facetiously asked the other lawyers if they wanted separate trials based on the "credibility of the grandmother."

When lawyer Lillian McEwen announced she was calling Rouse to the stand, a murmur of surprise went through the courtroom and nearly 100 people lined up outside the already packed courtroom as the news filtered through the courthouse.

Rouse is the only defendant who had been named by every prosecution eyewitness as being at the scene of Fuller's fatal beating, and he has been identified by several as having thrust a foot-long pole into Fuller's rectum.

Questioned by McEwen, Rouse calmly described spending the afternoon of Fuller's death with Charles S. Turner, one of the 10 defendants, and Taylor, who has not been charged in the case, touring his Northeast neighborhood, smoking marijuana and visiting arcades, carryouts and a recreational center.

Following the path described by Taylor but being less certain of the time sequence, Rouse told the jury that the three ended the afternoon at the alley after they saw a number of police cars.

Rouse explained to McEwen why he thinks two prosecution eyewitnesses -- both of whom have pleaded guity to lesser charges in exchange for testifying -- may have lied about Rouse's participation in the beating. He said Harry Bennett was angry with him because Rouse stole his girlfriend. Calvin Alston, he said, became upset with him because Rouse called him a "ding ding boy" when he heard that Alston had been raped in jail.

Under cross-examination from Assistant U.S. Attorney Jerry S. Goren, Rouse often gave confusing answers and sometimes was not certain about his movements. When Goren asked him to describe why police had stopped him earlier that day and frisked him for a gun -- part of his direct testimony -- Rouse seemed flustered and finally said, "You're trying to get me confused, aren't you?"

Goren pressed him further about the gun. Rouse initally described it as a blank pistol and then said it was a plastic gun that he found on the street but then threw away. He said he discarded it because it was the "first of the month." "People be robbing people on the first of the month . . . and police stop you for anything," Rouse explained.

In one of the more angry exchanges, Goren asked Rouse about showing up at his girlfriend's house the night of Fuller's death, allegedly with blood on his pants.

"Don't you remember your girlfriend asking you why you had blood on the bottom of your pants . . . and you said because you had been boxing and someone had hit you on the nose?" Goren asked. Rouse said he did not remember that.

Goren also attempted to portray Rouse as being unusually interested in the Fuller investigation. Rouse acknowledged that two days after Fuller's death, he asked a police detective what he knew about "the lady who was got killed in the alley." Rouse said he had heard from a friend that his name had "come up."

At the end of the day, Judge Scott ordered Rouse into "isolation" until his testimony can be continued Monday and ordered him not to talk to any of the codefendants on the weekend.

As Rouse testified, his mother, Emma Bratt, sat in the second-to-last row of the courtroom. "I always brought up my son to tell the truth," she said. "Now, it's in God's hands."