A girlfriend of one of the 10 young persons on trial for murder gave an eyewitness account yesterday of Catherine L. Fuller's death -- and a glimpse into a life of drugs and illegitimate babies for many youths in the depressed neighborhood where Fuller was beaten to death.

In a halting and nearly inaudible voice, Carrie Eleby, 17, told a D.C. Superior Court jury that she was the mother of two small children, including a daughter fathered by one of the accused, and that on the day Fuller was killed she had smoked some "loveboat," or PCP, with a friend.

The nine men and one woman accused of killing Fuller all live in the same Northeast neighborhood. Many had dropped out of school, fathered illegitimate children, used drugs and been convicted of other crimes.

Eleby's testimony did little to answer the central question of how a group of young people might come to be implicated in what has been called one of the most brutal killings in the District's history.

But her descriptions did lend some credence to speculation by many involved in the case that an environment of poverty and endemic despair about the future may retard development of social consciences among young people.

Often seeming unable to find the right word or phrase, Eleby described the day Fuller was killed as one spent rambling from bus to park to the houses of people whose last names or real names she did not know. On the way to the house of one of those friends, Eleby said she and a friend, whom she called "Smurfette," heard a scream coming from an alley.

"We came close a little bit . . . , " said Eleby, diverting her eyes from the rows of young persons on trial. "And they was beating on a lady."

In the most startling moment of her testimony, Eleby said Kelvin D. Smith, the father of her 4-month-old daughter, was among eight young persons -- including one who has already pleaded guilty -- whom Eleby said she saw attacking Fuller. Eleby previously had stated during a grand jury investigation that Smith was present in the Northeast alley but had not participated in Fuller's beating.

When Eleby implicated Smith, his lawyer, Greta Van Susteren, spun around in her seat and stared at her client.

Eleby, a scarf tied around her forehead as a headband, said she initially had lied about Smith's involvement because "I was pregnant by Kelvin Smith" at the time of her grand jury appearance. At that point, Smith bowed his head. He rarely looked at Eleby during the rest of her testimony.

Eleby's testimony followed several days of eyewitness accounts by two men who have pleaded guilty to charges in connection with Fuller's slaying. Although Eleby's testimony was far less coherent and complete, she corroborated several elements of the two previous accounts. She failed to implicate three of the defendants: Charles Turner, 21, Alphonso L. Harris, 23, and Felicia Ruffin, 17.

Ruffin, whom Eleby described as a good friend, so far has been implicated by only one prosecution witness in the case before Judge Robert M. Scott. Eleby said she did not know Turner and Harris, who were named by the two other witnesses.

In contrast to their cross-examinations of earlier witnesses, the three defense lawyers who questioned Eleby appeared to tread lightly. Eleby frequently seemed confused and frustrated by questions.

Eleby erupted angrily and tearfully when lawyer Lillian McEwen asked her to read one of her previous statements. Eleby refused and shouted at Judge Scott that she would not do it. After being admonished by Scott, Eleby was escorted from the courtroom crying.

During the break, Scott denied a motion by lawyer Wendell Robinson to remove Eleby as a witness and then was told by Assistant U.S. Attorney Jerry S. Goren that Eleby had trouble reading. When Eleby returned, Scott read the statement to her.