With his date with the electric chair less than 20 hours away, James Terry Roach, 25, a death-row inmate for eight years, was escorted into a cramped 8-by-10 visitors room. A phalanx of prison guards stood by. For an hour on Thursday morning, I visited with Roach in the one- story death house of the state penitentiary, a maximum-security complex of 1,300 inmates.

The Palmetto State's electric chair, complete with a backup generator in case of power failure, was a few steps down the hall. On Friday morning two hours before dawn, Roach would be strapped into it and become the 243rd person to be electrocuted by South Carolina since 1912.

Roach, sitting behind a tiny coffee table, had an expressionless face except for his darting eyes. They showed bottomless fear. He had flaxen hair, wide shoulders and skin with the kind of sallowness brought on by years of life without sun.

Roach, mentally retarded with an IQ of between 75 and 80 and suffering from the early stages of Huntington's Chorea, an incurable brain disease, spoke in a thick-lipped rural Carolina accent that at times was indecipherable in its monotone. This was no eloquent Caryl Chessman or Jack Abbott offering quotable social criticism of the death penalty. Roach, with simple words that a child would use, was a terrified, cornered human being. He personified fear, not evil.

I wanted to learn Roach's feelings about the families of the teen-age girl and boy whose 1977 killings he confessed to being involved in when he was 17. "I have prayed for those families," he said. "I can see what my family's gone through. I pretty well know they've been through hell too."

All of Columbia appears to have had hellish times since the bodies of Tommy Taylor, 17, and Carlotta Hartness, 14, were found Oct. 30, 1977. The victims -- athletic, motivated, life-loving kids and schoolmates at a private academy -- were from well-positioned families. Taylor and Hartness were parked in a family automobile in a city park on a Saturday afternoon when three strangers pulled up. Bullets from a small caliber rifle would soon kill Taylor and Hartness and put them on the national list of 19,120 recorded murders that year.

Roach's role in the murders has never been clear. Because he accepted the advice of a lawyer and, in a moment of courtroom confusion, abruptly pleaded guilty, a jury trial was not held. He was sentenced to the electric chair by a judge who had once voted in the state legislature for the death penalty. The judge acknowledged that Roach's guilt was mitigated by six circumstances, including no record of violence, his emotional and mental condition and his being a minor. It came out also that Roach, a passive dependent personality, was under the domination of an older ringleader. This was J. C. Shaw, a drug-using soldier from nearby Ft. Jackson who also pleaded guilty. He was executed Jan. 11, 1985. The third person at the killings was a boy of 16 who turned state's evidence and is now serving a life term.

Instead of talking about his legal case -- which had Mother Teresa, Jimmy Carter, Amnesty International and others offering public support because he was a juvenile criminal -- we discussed his life and values. I told him that after I had written about his appeals I had heard from a number of readers who expressed gladness that he was being executed. They said he fully deserved it. Roach replied: "They sayin' it 'cause they got no kid on death row. If the same people that wrote you letters, if their kid's on death row, you'd get letters different."

The stories he told of his childhood were the usual tales of blight and poverty that are as common to the people of death row as the bars that cage them. He dropped out of school, took "every drug there is," ran away from a home headed by an often-absent father and sick mother and became dominated by lowlifes.

The happiest memory for Roach was that he learned to read and write on death row. "When I first came here when I was 17, I couldn't write a letter home. I barely could write my name. . . . At one time they had teachers coming in (for) people who wanted to go to school. That helped me. Now at least I can write a letter home they can read. So I have learned a lot since I been here eight years."

Roach sensed the futility of hoping that any of his sorrow would be a consolation to the Taylors and Hartnesses. "For the last eight years," he said, "I know every time they ever hear my name or J.C.'s name in the paper I know that brings, you know, memories back. I have prayed for those families. . . . I'm sorry people are dead."

The opportunity to hold forth the joys of being born again in the Lord was present. But if Roach had had a religious conversion he didn't mention it. He had no interest at all, or no canny mind, to angle for sympathy. His feelings were uncamouflaged, in a guilelessness that may have been his nature or part of prison defeatism that he could not defend against after having lived a third of his life under a death sentence.

His world was the cell block he lived on, the only community he had had in his adulthood. When I asked if he could recall any pleasant experiences in his years of imprisonment, he replied: "Aside from me learning how to read and write, I know I got a lot closer to the people (on the cell block). I'd say the whole second tier -- they're like my brothers. That's how close I was to them."

On Tuesday of last week, Roach was separated from his community. He was brought from death row to a small brick building that has holding cells near the electric chair where he would stay for 72 hours. This sudden uprooting to a death row within a death row was the most traumatic experience Roach had had in prison: "I'm thinking once they get you here, this is it. I know it is it if you don't get no stay. This has been the worst thing, moving me over Tuesday morning."

This 72-hour period in the holding cells is policy. It is meant to acclimate the doomed man. Death shouldn't come abruptly. The long walk to the chair -- the last mile of the Cagney movies -- is here a brief trudge across the hallway. Witnesses, of whom there are four official ones, plus the warden, a doctor, two lottery-selected reporters, an uncle of Tommy Taylor and the all-important electrician, also had their acclimation. Two briefing sessions were given a few days before. As a prison official explained it, an execution isn't an everyday sight and "we don't want anyone to be shocked." As it turned out, Roach's body, witnesses reported, wrenched with the customary spasms and stiffenings. His trim 175-pound body took well the two 60-second surges. It was not as grisly as in 1944 when a 14-year-old black child took the first current and was seen to be weeping when the death hood jerked from his head.

When our conversation was ended, I thanked Roach for his time. I said he had many sound reasons to think well of himself. We shook hands, and I embraced him.

All that Roach had said to me suggested that the man South Carolina would soon be killing was not the boy they caught in 1977. Physiologists say that every seven years, the body renews itself. Emotionally and perhaps spiritually, Roach appeared to have had during his time on death row a similar transforming. It was another case of the state getting the wrong man. It wanted the old person but it killed the new.