The Subaru Outback, packed with six high school students free from summer school classes, sped along East West Highway on a warm afternoon last July with the radio playing, the car swerving from lane to lane and the teenage boys inside screaming.

"Stop!" someone shouted. "Slow down!" The car lurched from side to side.

"Everybody put on your seat belts!" someone yelled.

There wasn't time.

"It was like a roller coaster," recalled Hartley Abraham, 18, who had folded his six-foot frame into the station wagon's cramped back cargo compartment. "We kept going faster and faster."

Behind the wheel, Michael Schoenfeld, then 16, flashed a grin to Matthew Waymon, 16, his best friend who was sitting in the front passenger seat. They were passing cars, one by one. Then came the hill. And the curve. And more swerving. And a pickup truck.

Abraham grabbed onto a back-seat headrest and closed his eyes.

This inside-the-car account came yesterday during the first day of Schoenfeld's trial in Montgomery County juvenile court on charges that he caused the deaths of Waymon and another of his passengers, Irn Williams, also 16, and the pickup driver, John Francis Wert, 40, of Potomac.

Schoenfeld and three other passengers in his car were hospitalized for broken bones and, in one case, a collapsed lung. Abraham testified that he had a broken collarbone, femur and ankle.

Prosecutors said Schoenfeld's car crossed the center line, struck Wert's pickup, went airborne and flipped on its side before landing on top of Wert's pickup and another car.

Montgomery prosecutors have charged Schoenfeld with four traffic offenses and three counts of vehicular manslaughter, alleging that he caused the collision through "gross negligence" and reckless driving. Schoenfeld, now 17, has pleaded "not involved"--the juvenile court term for not guilty--to all charges.

The opening of the trial brought together in one courtroom families who have spent nearly a year grieving.

Schoenfeld's mother, seated behind him with his father, dabbed at her eyes as defense attorney David Driscoll asked the judge to remember that the collision happened in a matter of seconds, in a matter of feet.

Mothers and fathers, aunts, uncles and grandparents of Williams and Waymon sat on the packed courtroom benches and wept. Teenage friends held hands. Mary E. Wert, who wore her husband's wedding band on a gold chain around her neck, left the courtroom in tears when Abraham's account turned to the details of the impact.

"There's no doubt the results of the collision in question were tragic. As a result, there are parents who grieve the loss of their children, children who grieve the loss of a parent and a wife who grieves the loss of a husband," Driscoll told District Court Judge Eric M. Johnson, who is presiding over the trial.

But Assistant State's Attorney Marc Hall said that Schoenfeld had shown "bad judgment" by driving 68 mph--more than twice the posted speed limit--and "intentionally" swerving his car from lane to lane while continuing to speed up.

Several people who also were driving along East West Highway on July 14 testified that they saw the Subaru Outback careering from lane to lane before they heard the horrifying sound of metal crunching.

Schoenfeld's attorney told Johnson that his client was merely a young driver--he'd gotten his license just two weeks earlier--who lacked the experience to keep control of his car.

Even if Schoenfeld was speeding, Driscoll said, the teenager didn't commit the "outrageous and extraordinary conduct" required to prove the three manslaughter charges.

"The evidence will show this was not intentional, but inexperience," Driscoll said.

If found "involved," or guilty, of the manslaughter charges, Schoenfeld would face a maximum penalty of incarceration until he turns 21. The trial, which is open to the public, is expected to last most of this week.

The fatal crash raised questions about how old Maryland teenagers should be before they are allowed to drive. It was also the kind of collision that state officials said they want to prevent by requiring Maryland teenagers, as of July 1, to drive longer on both their learner's permits and provisional licenses.

CAPTION: "It was like a roller coaster," said Hartley Abraham, 18, a passenger in a car driven by Michael Schoenfeld that went out of control and killed three. Abraham testified yesterday.

CAPTION: Michael Schoenfeld, 17, is on trial on charges of vehicular manslaughter.