A Fairfax County jury deliberated for three hours last night without reaching a verdict in the case of one of the three young men accused of causing the fire that gutted Fort Hunt High School last December.

The Circuit Court jury, which was told that the fire was set because the three did not like the school's principal, will resume deliberations at 9:30 a.m. The jury is considering the arson charge against Timothey M. Greer, 19; the other two defendants are to be tried later.

Prosecution and defense lawyers agreed yesterday that the blaze, which caused $4 million in damage and closed the building for the rest of the school year, dislocating 1,745 students, was a result of the animosity that Greer and two Fort Hunt students had for principal James E. Manning.

"This is no boyhood prank. This is no act of school spirit. This is a malicious act that is done with the stupid motive that they didn't like Dr. Mannings," said Deputy Commonwealth's Attorney Steven A. Merril.

Testimony yesterday by Greer, the son of a two-star Army general, and Matthew Musolino III, 18, who also is charged with arson in the case, provided a first-hand account of the parties, drinking and planning that preceded the early-morning fire.

The jury of eight men and four women heard Greer described by the prosecution as the "wheel man" who drove the other two to the scene of the arson. It also heard Greer, who graduated from Fort Hunt last spring, testify that he had no idea that his two friends were going to do anything more to the school than break a few windows.

"It seemed to me it was just a put-on," Greer testified. "The only thing I expected was a little vandalism, breaking some windows."

Greer wore a brown sports jacket and a tie to court; his hair was cut much shorter than when he first appeared at the courthouse in January.

As related in court yesterday by Greer and Musolino, the partying that led to the fire began about 10 p.m. on Friday, Dec. 29, at the home of Robert Smithwick, 18, the third Mount Vernon teenager accused in the arson. Smithwick, who was then a reserve forward on the Fort Hunt basketball team, did not testify yesterday.

According to testimony, Greer and Smithwick drank several beers at Smithwick's house before deciding to drive in Greer's car to the District of Columbia, where friends on the Fort Hunt Rugby Club were throwing a party. There, Greer "played drinking games," trying to drink beer faster than his friends, and Greer said someone kept slipping hard liquor into his beer.

After the party, according to the testimony, the two Mount Vernon teen-agers drove toward home and stopped off at the house of their friend Musolino, a senior who had started for two seasons on the Fort Hunt football team. The three ate pizza and discussed their disdain for school principal Manning.

Manning, who has said the burning of the school was a personal loss and who testified yesterday, had already been the object of vandalism at Fort Hunt. In October, vandals cut down the school flag pole with a pipe cutter and rammed it through the window of Mannings's office.

That same month, Manning testified, he warned Greer for the second time in the semester to stay off school property when classes were in session.

In Musolino's house on the night of the fire, according to a statement that Greer gave police on Jan. 6, "someone suggested that we burn Manning's office, and we all agreed.

At about 1:30 a.m., Greer and Musolino testified, the three drove in Greer's car to Musso Service Station at 7400 Richmond Hwy., which is owned by Musolino's father. They filled a soda bottle and a whiskey bottle with gasoline, according to testimony, and Greer drove them back to Musolino's home a few blocks away where they picked up some ragged socks to be used as fuses for bottle bombs.

At about 2 a.m., they left for Fort Hunt High School, according to testimony.

On the witness stand yesterday, Greer maintained that throughout the discussion of burning the principal's office and during the trips to get gasoline and fuses, he thought the whole idea of arson was a joke.

"When they (Smithwick and Musolino) got out of my car, I told them the whole bit was crazy," Greer testified. He said Smithwick told him they were going to throw the gasoline away.

Musolino testified that he and Smithwick walked to the school's administration wing where Musolino "punched out" some windows near what he thought was the principal's office.

After breaking the windows, Musolino said he figured enough damage had been done. He said he then got angry with Smithwick, who, he testified, still wanted to start a fire.

I told (Smithwick) to get f - , and I walked away." Musolino said. He added that the next thing he recalled was Smithwick running past him for the car, saying, "The school's burning up."

Smithwich is scheduled to be tried on an arson charge in Circuit Court today.

Musolino, under a plea-bargain, has an agreement under which the prosecution will charge him with vandalism rather than arson in return for his testimony against Greer and Smithwick. Musolino testified that Greer warned him and Smithwick, after the fire started and they got into Greer's car, against calling the fire department for fear that someone "could identify our voices."

But Greer testified that Musolino was wrong. Greer said that even when Smithwick got into the car and told him the school was on fire, he (Greer) laughed.

"When I passed the school (the next morning) I finally took everything serious," Greer said.

Throughout yesterday's trial, which went to the jury at 5:30 p.m., Greer's defense attorney, Louis Koutoulakos, unsuccessfully attempted to describe to the jurors the Musolino plea bargain.

Greer, who is charged with a felony, faces a prison term of 2 to 10 years if convicted. A misdemeanor is punishable by a maximum of one year in prison and/or a $1,000 fine.

Judge Lewis H. Griffin ruled consistently yesterday that Musolino's bargain with the prosecution was not relevant to the charges against Greer.

Throughout yesterday's trial, Greer's father, Maj. Gen. Thomas U. Greer, sat quietly with his wife. The general, according to evidence presented yesterday, accompanied his son to the police station and was instrumental in urging his son to admit his involvement in the arson.

Gen. Greer is the director for management in the office of the Army chief of staff at the Pentagon.

The fire at Fort Hunt High began in the school records room and gutted most of the building before firefighters could respond.

In testimony yesterday, Greer and Musolino said the plan at the beginning had been just to burn the desk in the principal's office.

"It never crossed my mind that it (the fire) would destroy the school," said Musolino.

In closing arguments, prosecutor Merril pointed out that Virginia law does not recognize such limited intent.

"The fact that they did not intend to burn down the whole school is of no credit to them," Merril told the jury.