An autopsy performed yesterday on convicted spy Larry Wu-Tai Chin confirmed that the former CIA analyst, found early Friday morning in a Prince William County jail cell with a plastic bag tied over his head, died by asphyxiation, and officials have ruled his death a suicide.

Roger Ray, U.S. marshal for the Eastern District of Virginia, said the autopsy, performed at Fairfax Hospital by Northern Virginia State Medical Examiner Dr. James Beyer, found that the 63-year-old Chin died by asphyxiation, "which is consistent with the condition he was found in at the jail."

"I'm going to rule it's a suicide," said Prince William County Commonwealth's Attorney Paul B. Ebert, who conducted an investigation into Chin's death at the Prince William-Manassas Regional Adult Detention Center.

Chin, convicted Feb. 7 of espionage, conspiracy and tax evasion, was awaiting sentencing on March 17. Jail personnel found him at 8:45 a.m. Friday with a plastic bag tied over his head with shoelaces. Attempts to revive him proved fruitless and he was pronounced dead at 9:35 a.m.

Jail superintendent Stephan Kaftan said yesterday that Chin used a plastic garbage bag liner taken from a wastebasket in the jail's dayroom, adjacent to Chin's cell. The shoelaces came from high-top sneakers that Chin had recently bought in the jail's commissary, Kaftan said.

"Garbage trash can liners are normally used in the institution for sanitation and cleanliness," Kaftan said.

Chin's two sons, who asked that their first names not be used, said that their father had been writing to his wife Cathy almost daily since his conviction and had not indicated that he was depressed. They called the letters "upbeat."

"He was talking about writing his memoirs; he was talking about an appeal of his conviction ," said one son.

They said a sealed, stamped letter from Chin to his wife that was found at the jail Friday had been placed in the jail's mail system. Kaftan said he did not know where the letter was found, but that it had not been retrieved from Chin's single-bed cell.

The letter and other writings in Chinese that Chin left in his cell will be translated and "screened for possible national security information before they are released" to the family, Ray said.

Chin's sons said that the family is shocked by his death. "He's always been a fighter. I've never seen him to be depressed," said one son. They said their father was expecting a reporter for an interview on the day he died.

They also said that federal prosecutors had recently called their father's lawyer and asked if Chin, a former translator for the CIA's Foreign Broadcast Information Service, would agree to be debriefed by the CIA. Chin had agreed, but wanted his attorney present while it was taking place, the sons said.

"I can't confirm it," said Robert F. Muse, an attorney with the law firm that represented Chin at his trial. Muse said he could not specify what matters may have been part of negotiations with prosecutors.

A CIA spokeswoman said the agency had no comment on the report.

Jail superintendent Kaftan said that Chin, interviewed by jail medical staff Feb. 11, had "denied he had any intention of committing suicide," as a jail inmate had reported to officials there. Kaftan said Chin was not placed under a "suicide watch," as other sources had indicated Friday.

Medical examiner Beyer said that suffocation is not an uncommon manner of suicide and added that he has known of suicides by this manner "several times a year." District medical examiner Dr. Rak Woon Kim agreed, saying that the natural instinct to fight for air can be overcome, but that "it needs determination to die." It takes five to 10 minutes to become unconscious after the airways are blocked, Kim said.

Ray said Chin's body had been moved yesterday to an Alexandria funeral home.