The three youths accused of hurling rocks at cars on the Capital Beltway engaged in a "cowardly plan" to lure motorists to the side of the road so they could take better aim at their victims' heads and faces, a prosecutor charged yesterday.

"They weren't guilty of throwing at cars. They were throwing at people," said Prince George's County Assistant State's Attorney John Smathers, who described the May 27 scene when 24 passing cars were pummeled with large landscaping stones as they approached Indian Head Highway. Nearly 30 people were injured in the early morning incident, including 16-year-old Destiny Lynn Morris, of Hagerstown, Md., who lapsed into a coma when her skull was crushed by a rock.

Smathers said that John Lavon Burgess, 18, of Forest Heights, who went on trial yesterday, and his two friends tricked motorists into slowing down by waving their arms and signaling cars into the left lanes, a motion some drivers interpreted as a call for help.

One victim, Jeffrey Baker, of Alexandria, testified that an unidentified youth "looked right at me" before tossing a large rock "as if he were throwing a javelin" toward the driver's side window. "It seemed as if he were looking me straight in the eye," Baker said.

"There was no sense to it. Even a thief takes something for his own use. With this, there was no purpose. I only wish we could have our rocks back so we could hurl them at him," said John Robert Bruce Tillery, a Navy machinist stationed in Norfolk who sustained minor eye injuries.

Burgess is charged in a 90-count indictment, which includes charges of assault with intent to murder and disable and reckless destruction of property. Facing similar charges are Donnell Richard Petite, 18, whose trial is set for Dec. 10, and Maurice Edward Ford, also 18, who faces a Feb. 25 court date.

Burgess has pleaded not guilty to the charges. His attorney, James Joyner, waived an opening statement yesterday and declined to discuss his defense strategy. In cross-examinations of several police officers involved in the case, Joyner asked whether Burgess was coerced into making a statement to police or misled about the cooperation of the other defendants.

In a statement given to Prince George's County police at the time of his arrest, Burgess said he and his friends threw the rocks "just for fun" after seeing a movie and drinking two quarts of wine cooler to celebrate their high school graduation.

The rock-throwing began from an overhead bridge, then moved to both sides of the highway, Burgess said in the statement, which was introduced into evidence. He said he "just wasn't thinking" about possible injuries the rocks could cause.

As Burgess's non-jury trial began before Circuit Judge William D. Missouri, a parade of victims took the stand to describe the chaos that ensued between 2 and 3 a.m. May 27 when three figures emerged from the median strip and repeatedly pelted cars with rocks weighing from 5 to 15 pounds.

Some victims brought with them the gray rocks, ranging in size from that of a flat tissue box to a large, misshapen grapefruit, that had landed in their vehicles. They said they had kept the stones on office desks or in living rooms as reminders of the incident.

None of the victims could identify Burgess, who stared impassively at the front of the courtroom throughout the day. Police said they targeted him after an intensive investigation that involved neighborhood canvassing and interviews with more than two dozen suspects.

The drivers said that even after they pulled their cars over to assess damage, they saw in their rear-view mirrors other motorists being attacked. The rock-throwing lasted about 45 minutes, with disabled cars lining both sides of the southbound lanes and some dazed victims searching for help.

Byron Jeffrey, of Fort Washington, said he and another victim tried to chase the assailants after a rock pierced his windshield on the passenger side, fracturing his cousin's arm in three places. But Jeffrey said the assailants evaded them in some nearby woods.

James Palmer, of Ocean City, Md., described the horrifying crash when three rocks slammed into his pickup truck as he traveled toward Hagerstown to return Destiny Morris and her friends from a weeklong beach trip.

Palmer said he jumped from the car and ran toward the assailants, intending to fight them. But he said his girlfriend screamed for him to come back to the car because Destiny, who was sleeping in the crowded front seat with her head near the windshield, did not awaken after the impact.

"I wiped her forehead, and it just disappeared. It was just skin. Her whole hair was soaked with blood," he said.

Palmer said he flagged down a truck driver, who called for emergency assistance, and saw other approaching motorists being attacked.

"They were standing right on the guardrail -- just standing there picking off cars," he said.

In a dramatic moment, Destiny took the stand for several minutes and testified that she had no memory of the incident and could not remember the beach vacation she took with her best friend.

Her body trembled as two bailiffs helped her from a wheelchair into the witness stand. Destiny, who has been under treatment in a Wilmington, Del., hospital and recently has shown signs of improvement, stared at the floor and did not look at the defendant, who kept his eyes trained ahead.

Smathers said he called Destiny as a witness because she expressed a wish to testify and because he wanted to show the judge and the defendant the seriousness of the injuries.