George Pawlak remembers the reflection of the automobile headlights stabbing the late-night darkness as he and three teen-aged friends walked along the edge of the Fairfax County highway. He glanced to his left, and where 16-year-old John Svec had been walking a minute before, there was nothing but a blur.

"A blur, that's all I saw," Pawlak, 16, said yesterday in Fairfax Circuit Court during the first day of testimony in the involuntary manslaughter trial of Navy nurse Mary Ann Cronin, driver of the car that hit Svec on May 13. "The next thing I saw was John lying on the cement up the road."

Three days later Svec, a sophomore at W.T. Woodson High School, died as a result of a skull fracture suffered in the accident. Cronin, 34, of 3808 Persimmon Cir. in Fairfax City, was charged with involuntary manslaughter and driving while intoxicated. If convicted, she could face a sentence of up to 10 years in prison or up to one year in jail and a maximum $1,000 fine.

Yesterday's testimony before Judge Quinlan H. Hancock centered on the accounts of the three youths accompanying Svec the night of the accident near the intersection of Little River Turnpike and Shelley Drive in the Annandale area of the county.

Cronin, a lieutenant with a 13-year career as a Navy nurse, was dressed in a white Navy uniform with her cap placed on the defense table in front of her. She sat expressionless through most of the day-long proceedings. The small courtroom was packed with representatives of the anti-drunk driving group Mothers Against Drunk Driving, as well as members of the Cronin and Svec families.

Assistant Commonwealth's Attorney Jack A. Robbins said Cronin's black Datsun swerved off the main roadway and struck Svec, throwing him about 70 feet. Robbins said evidence shows Cronin had a blood alcohol level of .14 at the time of the accident. Under Virginia law, a driver is considered intoxicated when the level reaches .10.

But defense attorney Barry Murphy argued the four youths were "in a place where pedestrians shouldn't be," walking along a travel lane on the highway.

"They were dressed in jungle clothes, camouflage suits and they had been out in a pranking situation," said Murphy, adding, "If anything, this was an accident."

Pawlak and two other members of the group testified that they had donned Army camouflage costumes in an effort to see if they could sneak up to the house of a friend without being seen. They said the group, including Svec, had been to several friends' homes that night, and at one point had consumed small quantities of wine and hard liquor.

The teen-agers said none of the members of their group was intoxicated. Authorities familiar with the case said medical reports showed Svec had a blood alcohol level of .08, below the standard of intoxication for driving.

Two of the youths said they raced toward Cronin's car after they realized Svec had been hit.

"She looked shocked," said Douglas Anderson, 16. "I told her to get out of the car."

Cronin left the car and began administering first aid to Svec, according to testimony. But Fairfax County Police Officer Robert Smith said Cronin later failed several field-administered sobriety tests.

Testimony before the eight-man, four-woman jury is scheduled to continue today.