Inmates set fire to 14 buildings at Lorton Reformatory last July in hopes of forcing the early release of some prisoners after reading about overcrowded conditions at the prison, according to testimony in federal court in Alexandria yesterday.

The testimony by a former inmate came on the opening day of the trial of six men charged with arson, conspiring to riot and rioting for their alleged roles in the July 10, 1986, disturbance, which injured 32 people, left one inmate dead and destroyed four buildings at Lorton's Occoquan I and II facilities.

Government witness Judson Boyd, currently on parole, testified that the purpose of the uprising was "to get the count down and get people released . . . . The place was overcrowded . . . . They thought a lot of people would be released."

In his opening statement to the jury, Henry E. Hudson, U.S. attorney in Alexandria, alleged that the defendants -- Frederick Edwards, Michael Farrar, Matthew Fogle, Carl Henderson, Rodney Jenkins and Kevin Metts -- "began discussing their dissatisfaction with conditions at Occoquan" in early July.

They planned to burn down the Occoquan facility, Hudson said, "with the hope of making it less inhabitable by prisoners, and perhaps effect their early release."

Defense counsel have sought to portray the uprising as a spontaneous reaction to crowded conditions during a hot summer after publicity about overcrowding at the city-run prison complex, in southeastern Fairfax County. "There is no evidence of any conspiracy," defense attorney Donn E. Garvey told the jury.

But U.S. District Judge Albert V. Bryan Jr. has barred efforts by defense counsel to have government witnesses elaborate on living conditions at the prison.

"Overcrowding is not going to be used as a defense in this" case, Bryan said during yesterday's proceedings.

Earlier, he refused to allow a defense attorney to subpoena D.C. Mayor Marion Barry. The attorney, John Keats, had wanted Barry to testify about conditions at the prison.

David P. Decatur, former administrator of the Occoquan facilities, testified yesterday that there were 1,295 inmates there at the time of the uprising.

Boyd, 26, said that a group of inmates that included Jenkins, Fogle and Farrar had discussed burning down their dormitories after reading an article that "said Occoquan was a ticking time bomb." The inmates discussed this during recreational periods on the ball field, Boyd said.

He did not say where the article appeared, but said it was published about May 1986.

The day before the uprising, The Washington Post reported that a study by consultant Kathryn Monaco, who had been hired by the D.C. Department of Corrections, warned that overcrowding at the Occoquan facilities was so severe that a "major disturbance" could occur in "the near future."

After the July 10 uprising, Barry called it a "self-fulfilling prophecy based on various newspaper reports."

According to testimony yesterday, the disturbance began on the second floor of K dormitory, where about 90 prisoners slept in one large room.

The dormitory was not air-conditioned, and temperatures had been in the 90s for four days before to the uprising, according to the testimony.

Decatur testified that there was "mass confusion" when he arrived at Occoquan shortly after 1:30 a.m. Tear gas was used and four shots were fired by guards as they moved about 1,200 inmates to the ball field, he said. One inmate later died of gunshot wounds received that night.

Eight other Lorton prisoners have pleaded guilty to various offenses for their roles in the uprising. One defendant, Dennis Carter, is a fugitive.