A 20-year-old restaurant cashier told D.C. police that he strangled Marquita Vaughn, 18, during the raucous New Year's celebration at the Old Post Office Pavilion because she taunted his inability to respond to her sexually, according to a document filed yesterday in D.C. Superior Court.

Hearing Commissioner Roy M. Ellis ordered Alex T. Simmons of Wheaton held without bail on a charge of first-degree murder, based in part on Simmons' statements to police on Thursday. The hearing was the last step in an intensive two-day investigation of Vaughn's death.

Simmons entered a plea of not guilty yesterday.

Police said that their investigation of Vaughn's death was helped by a combination of tips, luck and evidence collected under the stairwell where the teen-ager's partially clad body was found about 2 a.m. on New Year's Day. The stairwell is at the southwest end of the shopping mall, within yards of the Blossoms restaurant where Simmons worked.

"It was obvious they [Vaughn and her assailant] were having a little party down there," said a police source familiar with the investigation. Officers found the body lying amid debris that included partially smoked marijuana cigarettes, a bottle of bourbon, cocktail glasses and an umbrella that eventually helped police identify two men Vaughn had been with earlier in the evening.

Simmons' lawyer, Allie Sheffield of the Public Defender Service, declined to comment about the case outside of the courtroom yesterday, as did several members of Simmons' family.

D.C. police said that Vaughn had met Simmons through friends at the annual New Year's party Tuesday, and that they went together to the secluded area, out of sight of the revelers.

The court document, written by D.C. homicide Detective Ronald Taylor, said that Simmons told police that the two had "preliminary sexual contact," and that Vaughn "taunted the defendant for his inability to respond to her sexual overtures."

"Defendant reacted by grabbing the decedent around the neck, and choking her until she stopped moving," said the detective's statement. "He said that as he held decedent by the neck the last time he kept thinking about her taunts and her challenge to him to prove himself. He said that as he choked her he decided that he would prove himself to her."

The D.C. medical examiner's office found that Vaughn's death "was caused by strangulation with great force for a continuous period of time ranging up to several minutes," according to the document.

Simmons, a small, thin man just over five feet tall, wore a tan, hooded jacket and dark slacks when he appeared in court yesterday.

Attorney Sheffield noted that Simmons has no previous police record, has lived in the Washington area his entire life, and has several family members living in this area.

More than 15 family members and friends, including the family's minister, attended yesterday's hearing. Simmons, who lived with his mother at 11212 Markwood Dr. in Wheaton, is a churchgoer interested in piano, saxophone and singing, sources said.

He graduated a few years ago from the Duke Ellington School of the Arts, the D.C. schools' program for talented musicians and artists.

He worked for four months last summer as a custodian at Montgomery College in Rockville, then took a job as a cashier at Blossoms, a bar-restaurant in the Pavilion. Blossoms was open for most of the New Year's celebration. Employes at Blossoms declined comment yesterday.

Police at first were stymied in identifying the body found under the stairs, but got a break when Vaughn's mother, Patricia Wright, reported her daughter was missing.

After Vaughn's family identified the body, police interviewed family members and Vaughn's boyfriend, obtaining information that led them to the apartment of a girlfriend of hers.

The friend said that Vaughn, accompanied by two men, had visited her about 8 p.m. New Year's Eve, police sources said. The friend declined Vaughn's suggestion that she accompany them to the Pavilion for the New Year's celebration, the friend told police. But she remembered that, while sitting on a couch in her apartment, one of the men was playing with an umbrella that had a distinctive handle.

When the investigators showed her the umbrella that had been found under the stairwell next to Vaughn's body, she said it was identical to the one the man had been carrying.

Meanwhile, police awaited laboratory results of an analysis of the evidence found under the stairwell. Numerous fingerprints were discovered on the bottle of liquor and the glasses, sources said, and investigators hoped that the prints, when run through a computer, would be on file and identify one of the men accompanying Vaughn.

Before the results came back, however, a tipster called police, according to sources. Two men had said they were with Vaughn the night she was killed, the tipster said, and the tipster then revealed their names.

Police went to the men's homes and persuaded them to come to the homicide office for questioning. Detectives also persuaded a third man, who was visiting one of the homes, to come along. That man was Simmons.

Simmons had told police he also had been at the Pavilion the night of the murder and the investigators hoped he might provide information about the other two, who were the prime suspects.

The breakthrough came when the two men said they had introduced Vaughn to Simmons and that the last time they had seen her was when she left them to be with Simmons, police sources said. When asked why his umbrella was found in the stairwell next to Vaughn's body, one man said that he had given it to her earlier in the evening.

Police then interviewed Simmons intensively for hours, finally concluding that he had been the man with Vaughn under the stairwell.