A former deputy U.S. marshal on trial in the slaying of a 20-year-old Navy seaman testified yesterday that the young man ignored several orders to get on the ground and continued to be verbally belligerent after the marshal shot him in the leg to disable him.

Arthur L. Lloyd, 54, charged with first-degree murder in the killing of Ryan T. Stowers, told jurors that Stowers then drove his Camaro toward Lloyd -- not away from him, as prosecutors contend -- and that he fired three shots at Stowers in self-defense.

The 28-year veteran of the Marshals Service, who retired after the shooting, took the witness stand yesterday morning as his team of three attorneys launched their defense in Montgomery County Circuit Court. It was Lloyd's first chance to tell his side of a story that had been told largely told by prosecutors, police and prosecution witnesses.

Lloyd's testimony, which highlighted his fear for his own safety and that of his children, directly contradicted that of prosecution witnesses in several aspects.

Prosecutors spent last week presenting a case that they say shows Lloyd had time to consider his actions before firing the shot that killed Stowers. They argue that Stowers was trying to get away from Lloyd when the federal agent shot him.

Lloyd, who was off duty at the time of the shooting, said that he, his wife and five children were shopping for Halloween costumes when he pulled off Rockville Pike into the Mid-Pike Plaza shopping center about 8 p.m. Oct. 29. He stopped, he said, only after his children and wife told him that someone was behind him, honking the horn and flashing the lights. He said Stowers quickly "jumped out" of his red Camaro.

"He just started swinging," Lloyd said. "He's swinging and yelling the whole time. It's like he's in a rage and I don't know why."

Prosecution witnesses last week testified that the men punched each other. Lloyd said that Stowers was the aggressor and that he landed the vast majority of blows.

Lloyd said that he fell to the ground and drew his gun after returning to his feet.

"I pull my gun out, and I tell him he's under arrest," Lloyd said. "He doesn't stop, for some reason."

So, Lloyd said, he shot Stowers in the lower leg. "I didn't want to kill him," Lloyd said. "I didn't want to kill anybody, for that matter."

He said Stowers called 911 and returned to his car, where he made some motions toward his glove box. Then, Lloyd said, he saw Stowers turn his steering wheel to the left -- toward Lloyd -- before turning it back toward the center.

"It's quiet, so I'm ready to put my weapon down," Lloyd said. "And then, all of a sudden, he turns his car toward me, and I just started shooting."

One of the bullets entered Stowers's back, severing his aorta, a medical examiner testified last week. Another shattered Stowers's rear windshield. A third blew out his left taillight. Stowers collapsed in the driver seat, and the car rolled into a store.

On cross-examination, Montgomery County Deputy State's Attorney John McCarthy got Lloyd to acknowledge that Stowers was not armed and did not assault Lloyd after being shot in the leg.

Lloyd disputed several aspects of prior testimony, contending that he never said, "I'm going to show him," before shooting Stowers and that he never told Stowers, "Give me the telephone, or I will shoot you again."

The defense also put on the stand a police officer from Antioch, Calif., who testified out of the presence of the jury that Stowers challenged the officer to a fight in 2003. Detective James Wisecarver testified that he was dispatched to a restaurant in June 2003 after a report of an assault. He discovered Stowers and another man hiding in the bushes. He ordered Stowers out, and Stowers cursed at him, Wisecarver said.

Wisecarver testified that he had to force Stowers to the ground and that Stowers was visibly drunk.

Judge Ann S. Harrington said she will rule today on whether the jury should hear Wisecarver's testimony.