Ten red cotton fibers from a plaid skirt like the one Melissa Brannen was wearing the night she vanished were found inside Caleb Hughes's car, Fairfax County's chief prosecutor said yesterday, during the third hearing this week in which significant clues to the state's case have been revealed.

Commonwealth's Attorney Robert F. Horan Jr. said that investigators have pieced together a duplicate of the outfit the 5-year-old girl wore to the Christmas party Dec. 3, 1989, where she was last seen. When Melissa disappeared from her Woodside apartment complex in Lorton, Horan said, she was wearing a blue Big Bird sweater and a red plaid skirt that came from the "Sesame Street" line sold by JCPenney.

"We're going to put on people who will testify they created this sweater," Horan said. He said they would describe how the clothing was made and testify to the trail it took from the mill to the middleman to JCPenney.

"The size of her outfit was 4 Toddler," Horan said. "Since the girl is no longer with us, we don't have her garment . . . . But we have a garment like it that was bought within a month after the outfit was bought for Melissa Brannen."

Hughes, 25, was indicted Nov. 19 on a charge of abduction with the intent to defile, a felony that carries a maximum sentence of life in prison. Horan has said that, after nearly a year of searching, he decided to charge Hughes with abduction rather than murder because no body has been found.

Horan has said that the state's case, which is scheduled to go to trial Feb. 25, will be mainly circumstantial and based on scientific evidence. The case has gripped the attention of area residents, who repeatedly saw televised home video footage of the young girl.

This week, components of the case have trickled into public awareness during hearings on discovery motions, in which Hughes's attorney has sought information on the evidence and experts Horan has assembled against his client.

On Tuesday, Horan said blue fibers found in Hughes's car appear to match fibers from the Big Bird sweater that Melissa was wearing. On Wednesday, Horan told a judge that an expert witness would testify that a human hair consistent with Melissa's was found in Hughes's car.

Defense lawyer Peter D. Greenspun, who is the Fairfax Bar Association president and was appointed to represent Hughes, said yesterday that he would not comment on the evidence.

On Wednesday, after Horan described the hair found in Hughes's car, Greenspun said, "A jury is going to look at the evidence in the courtroom, as it should. There is significant reason to doubt much of this evidence referred to during the course of legal arguments on legal issues . . . . It is unfair to draw any conclusion as to the strength of the commonwealth's case from . . . one hair."

Yesterday's hearing was prompted by a defense motion to compel the prosecutor to identify witnesses who will testify on how the fibers are made. Greenspun said he wanted the witnesses identified so that he could better prepare for the trial. "They insist on this shroud of secrecy," he said. "If they can prove it, let them prove it."

Greenspun has contended in motions that Horan has limited his access to physical evidence in the case. His motion yesterday was rejected by Circuit Court Judge Johanna L. Fitzpatrick.

Greenspun also filed a notice of alibi, in which he said that at the time of the abduction, "the defendant was at the Woodside Apartment Complex on Route 1 in Fairfax County, Virginia or allowing for differences in times and time estimates, may have been on Route 1."

The state has said the girl disappeared between 10 and 10:30 p.m. Dec. 3. Hughes was interviewed by investigators, and according to an affidavit filed in U.S. District Court in Alexandria, he could not give a clear account of where he was in the first two hours after Melissa's disappearance.

Hughes, who has sat silently during the hearings, has maintained his innocence.