Michael Keating took the witness stand yesterday in the the murder trial of a 23-year-old District man and gave a riveting account of being shot twice in the head at a Woodbridge town house last December.

"I told him 'Please don't shoot me, you can take my credit cards,' " Keating told a jury during the second day of Tony A. Mackall's capital murder trial in Prince William County.

Mackall is charged in the death of Mary E. Dahn, 31, who was shot in the head during a holdup Dec. 9 at the Woodbridge service station where she worked. He also is charged with robbery and felonious use of a firearm. Mackall, who at the time of the shootings was an escapee from a District halfway house, has pleaded not guilty to all charges.

Keating, one of 19 prosecution witnesses called yesterday, was shot about 30 minutes after the gas station holdup. Describing the incident, he said the gunman told him " 'Turn around, I'm not going to shoot you.' A few seconds later I heard the chamber . . . tremendous explosion . . . then I fell. I cried 'Oh God, oh God.' "

Keating, sports editor of The Washington Times, said he was knocked to the floor by the shot, and was ordered to get up by the gunman. As he did so, he said, "I turned to look at him . . . . The man shot again . . . . At that point I said the Lord's Prayer. I was expecting to die."

Asked by Commonwealth's Attorney Paul B. Ebert if the gunman was in the courtroom, Keating, 28, motioned toward Mackall.

Under cross examination from defense attorney Frederick A. Edwards, Keating acknowledged he had been unable to identify Mackall from police photographs and a lineup, but said that he later called police to say he had recognized one of the men in the lineup.

The prosecution spent much of the day trying to link Mackall, who was serving time for burglary and unauthorized use of an automobile, to a red Audi stolen from a District gas station and believed to have been used in the holdup in which Dahn was killed.

Gary Wheeler, a prosecution witness who said he was living in the Washington area at the time of the shootings, testified that on the day Dahn was killed, he helped a man, whom he identified as Mackall, work on the Audi near the Rte. 123 gas station where Dahn was employed with her husband Stephen.

Edwards pointed out that Wheeler was unable earlier to identify Mackall as the suspect, but Wheeler stuck to his testimony that Mackall was the man he had helped with the Audi.

Jay VanGelder, an identification specialist with the Prince William County police, testified that fingerprints taken from the Audi matched Mackall's prints.

Michael Randolph, an inmate with Mackall at the Prince William-Manassas Regional Adult Detention Center in January and February, testified that Mackall told him that he shot Dahn after a struggle and that "she deserved it."

Circuit Judge Herman A. Whisenant Jr. denied most motions by Mackall's two-man defense team, including their objection to a demonstration, with a styrofoam mannequin and a long needle, of the path of the bullet that killed Dahn.

"I would like the record to reflect that we are listening to noises as the needle is pushed into styrofoam," defense attorney Ronald Fahy said.

The day began with the testimony of Stephen Dahn and one of the couple's two daughters, April, 6, who was at the service station with her parents and little sister the night her mother was killed.

As Ebert led the blond youngster through the events of that night, he asked her: "Do you have a mommy?"

"No," the little girl responded.

"What happened?" he asked.

"Dead . . . shoot in the head. Mom was bleeding under her head."

"Did you see her eyes?" Ebert asked.

"They were all watery."