Arthur Miles, the 16-year-old youth who admitted taking part in the ambush slaying of a pizza delivery man last April, was convicted of first-degree murder in Prince George's County last night, despite his contention that the pistol used in the killing fired accidentally.

Miles, tried as an adult, was one of two persons charged in the death of Domino's Pizza employee Carl A. Krogmann, 25, of Bethesda.

Police said the second suspect, Roland H. Jeter, 18, ordered a pizza by telephone April 7 to lure the delivery man to an unoccupied house in Largo, where Jeter and Miles waited to rob him at gunpoint.

In a Circuit Court trial that began Tuesday, Miles's attorney, David Simpson, followed a strategy he hoped would result in convictions only for involuntary manslaughter or second-degree murder.

Had Simpson succeeded, his client would have faced a sentence of up to 30 years in prison.

With last night's verdict, Miles, son of a District police officer, faces a possible life term.

He was jailed pending sentencing Oct. 1.

"We feel very sorry for the Miles family, but were also very happy that justice was done," said Krogmann's father, Charles.

The case gained wide attention after Miles and Jeter were arrested, when District Court Judge Gerard Devlin allowed Miles to be released on $75,000 bond, pending the outcome of his trial.

Angered by the move, Krogmann's family launched a much-publicized campaign for Devlin's ouster.

Circuit Court Judge Jacob S. Levin subsequently revoked Miles's bond. But the Maryland Court of Special Appeals ordered it restored last month, ruling that Levin appeared to have been influenced by public opinion.

Because Miles confessed to police after his April 9 arrest, Simpson's best hope in the case was to avoid a life sentence for his client by convincing the jury that he was guilty of second-degree murder or involuntary manslaughter, but not first-degree murder.

Achieving that goal meant he had to successfully argue two points: that the gun had gone off in Miles's hand accidentally, and that the shot fired before the planned armed robbery actually had begun.

Miles testified Wednesday that the gun went off accidentally as he was moving to surprise Krogmann.

The jury, apparently believing him, acquitted him of first-degree premeditated murder.

But Simpson also had to raise doubts in jurors' minds about whether an attempted armed holdup was in progress when the gun went off.

Under Maryland law, if the jury found that Krogmann died while the victim of an armed robbery attempt -- or any felony -- Miles stood to be convicted of first-degree felony murder, even if he did fire the shot by accident.

In response to this, Simpson said that neither Miles nor his alleged accomplice had had a chance to demand money from Krogmann before the pistol went off.

He argued that the planned holdup never advanced beyond the conspiracy stage, and noted that conspiracy is not a felony in Maryland.

But the jurors apparently decided that the conspiracy ended and the attempted robbery began when Miles and Jeter allegedly entered the unoccupied and began waiting for the delivery man.

They convicted Miles of first-degree felony murder, attempted armed robbery, conspiracy and two handgun charges.

Jeter, 18, is scheduled for trial next month.