Alton Alonso Best, a 31-year-old District man, acknowledged yesterday that he beat and strangled a woman in a van owned by a D.C. police officer before dumping her battered body in a Northeast alley.

Best pleaded guilty in D.C. Superior Court, with D.C. Superior Court Judge Reggie Walton presiding, to second-degree murder and sodomy in the Jan. 15 death of 20-year-old Janice Elaine Morton, whose death received widespread attention because of its similarities to the unsolved slayings of five women whose bodies were found in a wooded field in Suitland.

Police in Prince George's County and the District have since said they have been able to establish links between three of the Suitland victims and Best, but have found no direct evidence tying Best to the Suitland slayings. Best's lawyers have denied any involvement by their client.

Prince George's County police said yesterday that Best was still a prime suspect in their investigation.

Best remained expressionless yesterday as a federal prosecutor described him as a man with a history of using force in sex and demanding sex for cocaine.

"The defendant frequently stated that no one would get coke {cocaine} from him without having sex with him," prosecutor Charles Hall said. Morton, who lived in the District, and the five Suitland victims appeared to have been sodomized before being strangled or fatally stabbed and most of them appeared to have been drug users, police have said.

Apparently surprised by the latest revelations, Best's lawyer Paul Leder said he had "never heard anything" to support the allegations about Best's character and that he planned to challenge them at Best's sentencing July 22.

Best pleaded guilty in exchange for the government's agreement to drop first-degree murder and rape charges in connection with Morton's death and a separate cocaine charge. Best could be sentenced from 18 1/3 years to life in prison.

Best's decision to plead guilty once he is sentenced, apparently frees prosecutors to call Best to testify before a grand jury investigating the actions of his nephew and the owner of the van, D.C. police Officer William A. Armah. Armah, who has been placed on administrative leave with pay pending the outcome of the investigation, has told police investigators that he cleaned blood from the van shortly after Best returned it to him Jan. 15. Best, he said, attributed the blood stains to injuries incurred by a friend.

Armah flashed his police badge when he was pulled over by Prince George's County police during a well-publicized surveillance for a black van, in which a witness reported seeing one of the Suitland victims.

Hall yesterday described the early morning hours preceding Morton's death as a moving party in search of cocaine. He said Morton, who had just met Best that morning at the home of a mutual friend, eventually agreed to go with Best in a black van to buy more cocaine. Morton's nude and battered body was found later with a brassiere tied tightly around her neck.

Staff writer Keith Harriston contributed to this report.