CONWAY, S.C. -- Minutes after the decision, the guards brought Limmie Arther, a convicted murderer with an IQ of 65, to a small back room in the Horry County jail to talk with his lawyer.

Experts on mental retardation had spent that day testifying that the 28-year-old sharecroppers' son had the mentality of a 10-to-12-year-old, at best, and that he could not remember his lawyers' names or recite the alphabet.

Last month Arther was sentenced to die in South Carolina's electric chair for killing his crippled 65-year-old neighbor with an ax and stealing his Social Security money. On Friday, the judge who had imposed the death sentence refused defense lawyers' plea to reduce Arther's sentence to life or grant him a new trial.

One of Arther's lawyers, John Blume, asked Arther how he felt about the result.

"I ain't too sure . . . , " Arther said, smiling. "I feel good anyway . . . got a new trial."

"Limmie, he didn't give us a new trial," his lawyer replied, wincing at his client's apparent failure to understand what had just happened to him. "This means we're going to have to appeal it. You know what appeal means?"

"Yes, sir," nodded Arther, the 17th of 18 children raised in a tiny, tin-roofed shack amid the tobacco fields of rural Duford, near Myrtle Beach.

The case of Limmie Arther poses the troubling question of whether the death penalty may be imposed on murderers who are mentally retarded -- or whether, as Arther's lawyers contend, the Eighth Amendment prohibition against cruel and unusual punishment bars their execution.

"It's just wrong to execute people whose understanding of the world is that of children," said Arther's chief lawyer, David Bruck, who has represented more than 30 defendants in capital cases.

"A 10-year-old or 11-year-old knows that it's wrong to kill. And he also knows that it's punishable. An adult who is operating at that mentality still deserves to be punished," Bruck said. However, he said, "The death penalty is an absolute punishment. And if it is to be imposed at all, it should be imposed on people whose sense of responsibility and judgment is such that they fully appreciated the seriousness of what they were doing."

But prosecutors in Arther's case -- and other advocates of capital punishment -- argue that, as long as mentally retarded offenders understand the criminality of their acts and are competent to stand trial, their low intelligence should not shield them from execution.

"There is an abundance of evidence in the record to show the defendant knew what he was doing, knew the criminality of his act, knew the difference between right and wrong," argued Assistant Horry County Solicitor Debbie Owens, whose boss, Solicitor Jim Dunn, announced his election bid standing next to the state's electric chair. Prosecutors have not conceded that Arther is retarded, but they presented no evidence to rebut the defense witnesses.

Defenders of a death sentence for Arther also point to the brutality of the murder and to Arther's prior criminal record, including five house break-ins, and his guilty plea to involuntary manslaughter in the stabbing death of his older brother, who attacked Arther with a two-by-four.

"The mere fact that he is retarded should not save him from the death penalty," said Fordham University law Prof. Ernest van den Haag, a champion of capital punishment. "If you are so retarded that you didn't know what you were doing or did not know that it was wrong, then you cannot be held guilty. If the court decides you were not so dumb, I cannot see any reason why the usual penalties should not apply."

The Supreme Court has never squarely addressed the issue. And Arther's case could become the one in which the justices decide whether executing the mentally retarded is constitutional. If Arther's death sentence is upheld, his execution would be the first since 1976 -- when the Supreme Court permitted capital punishment to resume -- of a defendant whose retardation was an issue before the judge or jury imposing the sentence.

Mental retardation, however, is not unusual among the 1,901 convicts on death row. A survey by the Clearinghouse on Georgia Prisons and Jails, a group that opposes the death penalty, found that at least 250 prisoners nationwide had IQs below 70, the accepted cutoff for mental retardation, and that 15 percent to 20 percent functioned at a subaverage intellectual level, with IQs in the low 70s or below.

Of 77 murderers executed since capital punishment was reinstated in 1976, at least five were diagnosed as mentally retarded or borderline -- but the issue of their mental capacity was raised too late in the process to stop their execution.

"Until now, the issue has been tangled in procedural technicalities having to do with the fact that retardation was discovered late in the legal process," Bruck said. "There are no technicalities in this case. This case simply presents the question of what is right and what is wrong."

Arther was raised in what his high school principal described in court as "the most barest conditions in which a family could exist," a weather-beaten three-room shack without running water, its broken windows covered over with tattered plastic sheeting. His parents often kept their children out of school because the children had no shoes. At a hearing last month, Arther's mother could not remember what number Limmie was among her "18 head" of children.

Taken to view the dilapidated homes of both Arther and the man he murdered, William (Cripple Jack) Miller, Horry County Circuit Judge John H. Waller Jr. remarked that they would have been "better off under slavery," because someone would then have been responsible for their care.

Even within that impoverished environment, Arther was always different, always slower than the other children. Jessie Miller Williams, who taught Arther in the third grade, when he was 10, testified that her "ultimate goal" that year was to teach him to write his name. She failed.

"He tried," Williams said. "He could remember some letters, and those -- sometimes he would put some of them backwards, and some he would have forward." Arther dropped out of school at 16, still unable to read or write, living with his parents and eking out a bare existence working in the tobacco fields and picking up pecans.

The crime for which Arther has been sentenced to death occurred on New Year's Eve, 1984. Arther's sister Marilyn drove him, Miller and Miller's wife, "Miss Katie," into town. "Miller cashed his Social Security check, paid some bills and bought two half-pints of liquor, which he and Limmie Arther drank behind a local store.

Marilyn Arther dropped Miller and her brother at the Miller's house. Limmie Arther said he was going to chop some wood. When Miller's wife returned a few hours later, her husband was dead. A bloody ax was lying nearby. In a washtub outside the Miller shack, police found Limmie Arther's bloodstained shirt. At the Arthers' home, they discovered Limmie hiding in the attic, his bloody boots sticking out of the rafters and $100 in his wallet.

When questioned, Arther first told police he earned the money selling pecans, then switched his story and told them he stole it from his father. When Leroy Arther disputed that, Limmie changed his story again and said he had taken the money from Miller earlier that day.

Arther did not testify at his trial.

To prosecutors, the fact that Arther hid after the murder and lied to police, demonstrate that he understood what he had done. "If he didn't understand the criminality of his act after he killed 'Cripple Jack' Miller, he wouldn't have had the sense to go hide in the attic or the ability to create a story and to change it," Owens said after Waller refused to reconsider his ruling.

"The death penalty was warranted in this case," she said. "This defendant has an extensive prior record, five convictions for burglary and larceny, and the brutality of the crime that he committed -- an ax murder on a defenseless, crippled man."

Arther's manslaughter plea in his brother's death was not used as evidence at the trial. And his lawyers say Arther acted in self-defense in that case.

From the defense viewpoint, Arther's "pathetic" attempt to escape responsibility by hiding and lying is evidence that he is not a savvy, street-smart criminal. "He took his bloody shirt and left it soaking at the scene of the crime. There he is hiding in the attic with his feet sticking out. Good grief," Bruck said. "If that's the crime of a mature criminal, I think the job of our law-enforcement agencies would be a great deal easier than it is."

Friday's hearing focused on how mental retardation can affect offenders and on the degree of Arther's disability. Dresssed in a blue cotton shirt, jeans and blue sneakers, Arther watched intently, his expression rarely changing, as witness after witness described his retardation. With an IQ that has tested at 65 from elementary school days through prison, Arther falls into the category of "mildly retarded."

Owens stressed that point, but John Beckley, executive director of the Association for Retarded Citizens of South Carolina, said the label "mild" is misleading. "Why don't we talk about amputation and say that a person is mildly amputated if they lost one leg," he said.

"Limmie Arther is without a doubt mentally retarded," said University of New Mexico Prof. Ruth A. Luckasson, an expert in mental retardation and criminal offenders.

Luckasson described asking Arther to recite the alphabet. "He got a very proud smile on his face, and in a weak, child-like voice he started to sing the nursery rhyme," she said. "He got to G, left out a few letters, after P the letters were totally garbled and out of order."

Far from realizing that his best chance for avoiding execution is to appear as unintelligent as possible, she said, Arther seems to think that the more he learns to read and write, the better off he will be. "I think he believes that the fact that he can't read is what got him the death sentence," she said. Prison officials have described Arther as a well-behaved, model prisoner.

Waller, in refusing to reconsider his imposition of the death sentence, said he was "not insensitve to mental retardation" but that he "bit the bullet and did what I thought was the thing to do according to the law" in sentencing Arther to death. Arther's initial death sentence, handed down by an Horry County jury in 1985, was overturned by the South Carolina Supreme Court.

In an interview as he ate his lunch of turkey sandwich, cooked carrots and black-eyed peas in the Horry County jail, Arther was asked what it would mean if he were executed.

"What happens? That's a tough one . . . . ," said Arther, who looks barely out of his teens. "For one thing, that learning what I just learned, what I learned in {the penitentiary} that wouldn't amount to nothing . . . . And my GED {high school equivalency degree}, I wouldn't see no GED. I wouldn't get my GED."

Asked to describe what had happened in court that morning, Arther showed little understanding of the testimony.

"The witnesses was coming in. All right. They was saying I was mentally retarded. They was trying to get the judge to understand that I am retarded. Um. I don't understand a whole lot of what was going on."

"Why would he care about someone being mentally retarded?" asked Bruck, who sat in on the interview.

"I don't know that . . . . Most of the words, you know, I had to listen real close, because, you know, I had to catch on one word, and the next word I have to try to catch on that, and I get lost very quick . . . . It's not good though. It's bad. It's bad to be retarded."