Tony A. Mackall was convicted of capital murder yesterday in the shooting death of a Woodbridge gas station attendant last December, a crime committed while Mackall was an escapee from a D.C. Department of Corrections halfway house.

After deliberating two hours, the Prince William Circuit Court jury found Mackall, 23, guilty of fatally shooting Mary E. Dahn in the head during a holdup at the Rte. 123 service station where she worked. Mackall also was found guilty of robbery and use of a firearm in the commission of a felony.

The jury sentenced him to life imprisonment on the robbery charge and two years on the weapons charge.

Jurors will meet again today at the courthouse in Manassas to begin deliberations on whether to sentence Mackall to death or life imprisonment on the capital murder charge.

Circuit Judge Herman A. Whisenant Jr. will impose sentencing at a later date. Under Virginia law, he may reduce the jury's sentence but may not increase it.

Mackall, who had pleaded not guilty to all the charges, was convicted of shooting Dahn, 31, during a Dec. 9 holdup at the gas station where she and her husband Stephen worked. Stephen Dahn and the couple's two young daughters were at the service station at the time of the shooting.

Prosecutors said that Mackall crashed his stolen car while fleeing, and that about 30 minutes later he shot Michael Keating, sports editor of The Washington Times, at a nearby town house and stole Keating's car. Mackall faces trial later this month in the shooting of Keating, 28.

After the guilty verdicts were handed down yesterday, Mary Dahn's aunt said the family has yet to overcome the shock of her death.

"It's just been horrible," said Jane Graham of Woodbridge. "I'll be glad when it's over so we can put the past in the past.

"I never thought seriously about what one should do to one who commits a crime such as this," she added, tearfully. "I'm for the death penalty. He killed my niece. He took my sister's only daughter."

Keating, who testified on Tuesday about being shot twice in the head, said yesterday: "You don't ever really get over something like this. It has been 11 months now, and not a day has gone by when I didn't think about it."

In his closing arguments in the three-day trial, Commonwealth's Attorney Paul B. Ebert told the jury that the evidence showed that Mackall was guilty and a "dangerous man."

Stephen Dahn and Keating had testified that Mackall, who had been serving time at the halfway house for burglary and unauthorized use of an automobile, was the gunman in both shootings.

In his closing statements, defense attorney Kenneth A. Edwards accused the prosecution of appealing to the jury's emotions.

Much of Ebert's case consisted of heaping evidence that had no bearing on the case, Edwards said. He also tried to discredit the identification of Mackall by the three witnesses.