A Prince George's County judge or jury will decide next month whether John Kevin Johnson of Accokeek, convicted of first-degree murder early yesterday in the rape-slaying of a 13-year-old Southeast Washington girl, will be sentenced to die in Maryland's gas chamber.

After more than seven hours of deliberation, a jury of seven women and five men found Johnson, an unemployed 26-year-old laborer, guilty of eight offenses, including first-degree murder, kidnaping and rape in the death of Arlene Flowers, whose body was found in a southern Prince George's creek last March. The verdict came shortly after midnight in Circuit Court in Upper Marlboro.

Johnson sat calmly with his attorneys as Judge Audrey Melbourne scheduled the sentencing process to begin on Nov. 8. Defense lawyers Darlene Perry and Edward Camus have the option of having the jury or Melbourne decide on the sentence.

"I'm still in shock," said Ada Flowers, the murdered girl's mother, who sat through three weeks of often vivid testimony on her daughter's ordeal and death.

According to key prosecution witnesses, Johnson bragged about having abducted Flowers from Southeast Washington and taking her to a trailer in rural Accokeek where he and a friend repeatedly raped her. He then took her to a bridge near Mattawoman Creek and shot her in the back at close range, according to the witnesses' recollection of Johnson's story.

"I don't know what the chances are, but I'm hoping he gets the death penalty," the victim's mother said.

The Johnson case is the fourth in which Prince George's prosecutors have sought a death sentence since the state's revised death penalty law went into effect in 1978. The three previous attempts failed, with the defendants receiving prison sentences. County prosecutors, who keep a poster-size chart of the complicated death penalty statute on the walls of the state's attorney's office, are hoping they will succeed in getting the death penalty for Johnson.

Assistant State's Attorney David Simpson said "it was important" to the prosecution that the jury convicted Johnson of all eight charges against him. But he said the sentencing phase is "a whole different ball game."

Once a defendant is found guilty of first-degree murder, the judge or jury considers a list of possible aggravating circumstances, including whether the murder was accompanied by other crimes such as rape. These circumstances are weighed against mitigating factors, such as whether the defendant was under the influence of drugs or any other circumstances the judge or jury finds relevant.

Last week a Baltimore County jury rejected the death penalty in the kidnaping, rape and murder of Frostburg State College student Stephanie Roper.

"To have 12 people say they will kill someone is very, very difficult," Simpson said. "It's extremely emotional when a man is up there pleading for his life," he added.

The only alternative for the judge or jury to the death penalty is life imprisonment. Depending on the number and severity of additional crimes of which a defendant is convicted and whether the sentencing judge makes the sentences run concurrently or consecutively, a prisoner with a life sentence may be eligible for parole in as few as 12 years. Jack Ronald Jones, 26, who was convicted in the Roper slaying last week, will be eligible for parole in 12 years because his sentences were made concurrent.