The investigation of the brutal slaying of a graduate student from Boston took a new turn on Thursday when a Queens judge approved a request by prosecutors to put the main suspect in the case in a lineup in a separate sex assault investigation.

District Attorney Richard A. Brown said in a statement that Darryl Littlejohn, 41, would be placed in the lineup in connection with a sex attack on Oct. 16, 2005 in the Forest Hills neighborhood. He declined further comment.

Littlejohn, who had been held on Rikers Island on a parole violation, appeared briefly in court before police took him into custody. His lawyer, Kevin O'Donnell, later emerged from the 112th Precinct stationhouse and said his client had not been picked out of the lineup. Police had no immediate comment.

Earlier, O'Donnell told reporters outside court that Littlejohn "absolutely maintains his innocence."

The parolee "feels like a scapegoat," the lawyer said. "He's upset. He knows his face has been published everywhere across the country" — a reference to a mug shot released earlier this week by authorities.

A law enforcement official told The Associated Press on Thursday that the Queens case was one of three unsolved sex attacks — including one more in Queens and one on Long Island — that may be linked to Littlejohn. All of them involved a man who abducted his victims late last year using a van, said the official, who spoke on condition of anonymity because the investigation had not been completed.

Littlejohn is not charged in the killing of Imette St. Guillen, 24, whose naked and bound body was discovered on Feb. 25. But investigators have increasingly focused on him in recent days, checking for evidence at the Manhattan bar where he worked, along with his Queens home and his blue van.

The suspect was a bouncer at The Falls bar, where St. Guillen was last seen alive. A manager at the bar has told police he ordered him to escort her out of the bar when she stayed sipping a drink past the 4 a.m. closing time; he recalled hearing the pair arguing before they disappeared through a side door.

Sometime during the next 17 hours, the student at John Jay College of Criminal Justice in Manhattan was raped, strangled and suffocated. Her body was found in a remote section of Brooklyn with a white sock stuffed in her mouth, and her head wrapped with packaging tape.