A Baltimore man was in critical condition yesterday at a District hospital after he was arrested earlier in the day for attempting to scale the White House fence and then tried to hang himself in his cell at a District police station, authorities said.

Robert E. Watson, 24, of 839 Herndon Ct., was placed on a life support system at Georgetown University Hospital, officials said, after the incident that began when Secret Service officers stopped him as he allegedly tried to climb the fence on East Executive Avenue.

A D.C. police source said that the suspect, who was not armed when apprehended by the Secret Service about 1:20 a.m. yesterday, was taken to the 2nd District police station, at 3320 Idaho Ave. NW, on a charge of attempted unlawful entry. While being interviewed there by the Secret Service, he indicated he did not feel well and about 3 a.m. was placed in a holding cell with a commode, the source said.

There were no other prisoners in the station's four holding cells, the source said.

The cell door was locked and when a Secret Service officer went to the cell about 15 minutes later to ask the suspect a question, sources said, he was found hanging from a cell bar by his shoelaces.

"From what we understand, there was nothing to indicate that the individual was an immediate danger to himself or someone else or that he possessed suicidal tendencies," said D.C. police spokesman Lt. William White III.

Members of Watson's family, interviewed at the Brooklyn Homes public housing project in Baltimore, where Watson lived with his mother, said they do not believe Watson tried to climb the White House fence.

His mother, Shirley Watson, and a sister, Dawn Watson, said he had no history of mental problems, but the sister said he had a drinking problem and recently had begun taking drugs.

The family said he had not been in trouble for about six years. At that time, he was incarcerated for about 30 days in Prince George's County for drunk driving. "He was scared of jail . . . terrified," his mother said.

"He swore he'd rather die than go back to jail," said Dawn Watson, 25, adding that he said he would "kill himself" if he was jailed again.