John Kevin Johnson, convicted of raping and murdering a 13-year-old Southeast Washington girl, yesterday calmly asked the jury that will decide whether he will go to Maryland's gas chamber to spare his life.

Johnson, a 27-year-old farm laborer and mechanic from Accokeek, held a yellow legal pad as he took the witness stand and told the jurors he was "pleading for my life."

"I am deeply sorry for what happened . . . for what is lost to the family . . . There is nothing else I can really do, nothing that can be done to bring" the girl, Arlene Flowers, back. He said he believes he can be useful in prison, counseling younger prisoners. "Maybe I can help someone else," he said.

One juror cried audibly and another wiped her eyes with a handkerchief as Johnson addressed them. Moments later the jury, which last month convicted Johnson of rape, murder and seven other offenses, left the circuit courtroom in Upper Marlboro to begin deliberating the question of whether he should be executed or sentenced to life in prison.

The jury was still deliberating early today.

The girl was abducted on her way home from a store last February, taken to Johnson's mobile home in Accokeek and sexually abused repeatedly before being shot in the back with a sawed-off shotgun, according to trial testimony. Her body was found 10 days later in a creek in southern Prince George's County.

Among the spectators in the courtroom yesterday was Roberta Roper, whose daughter, Stephanie Ann, 22, was raped, shot, beaten with a chain and set afire last April. Two men have been convicted of murder in that case and were given life sentences; under Maryland law they will be eligible for parole in about 12 years.

Outrage over those sentences led to the formation of the Stephanie Roper Committee, and Arlene Flowers' mother, Ada, recently joined it. Mrs. Roper spoke to Mrs. Flowers in the courtroom yesterday "as one victim's mother to another," she said.

Before Johnson made his final plea yesterday, defense attorneys Edward Camus and Darlene Perry argued that the death penalty is morally wrong, that life imprisonment would be punishment enough for Johnson and that he stood no chance of being paroled before he dies.

"Killing is cruel, killing is unusual, in a civilized society," Camus said.

"If Arlene Flowers were in here today, and she is -- she's in our hearts -- would she say 'Kill Him' or would she say 'I have suffered violence enough, enough is enough' "? Camus asked the jury.

"Let her memory not be clouded by the killing of another human being," the defense lawyer said.

Assistant State's Attorney David Simpson dismissed any argument that Johnson could be useful in prison, noting that Johnson has been charged with attempting to hire a man, who turned out to be an undercover police officer, to murder the three principle prosecution witnesses at his trial. Johnson is scheduled to stand trial on that charge next month.

"Even in the confines of the jail, he is a very real threat," Simpson said.

Simpson told jurors that the possibility always remains that Johnson could be freed on parole in 12 years, and added that he has been convicted of two armed assaults on women and a firearms violation. "The best barometer of future behavior" is previous behavior, he said.