It is the evening of April 4, 1968. The Rev. Martin Luther King Jr. leans over a balcony railing at The Lorraine Motel. The crack of a single shot from a high-powered rifle shatters the air.

Suddenly, he's gone.This much is clearly documented. But who killed the 39-year-old civil rights leader and winner of the Nobel Peace Prize?

James Earl Ray, the small-time thief who pleaded guilty, has spent the past 20 years trying to prove he didn't do it. He talks of a shadowy "Raoul."

Other principals in the case hold widely varying opinions: Ray's attorneys disagree on whether he was the triggerman; the prosecutor acknowledges he wasn't confident about the case; U.S. Rep. Louis Stokes, D-Ohio, the chairman of a congressional committee that studied the assassination, says he still concurs with the committee's findings that Ray may have been part of a larger, unsolved conspiracy.

The questions remain. What of the cigarette butts found in the getaway car given that Ray did not smoke? What of the clothing in two sizes in the car's trunk?

The fatal shot came from a communal bathroom at the rear of a flophouse across a narrow street from The Lorraine Motel. Ray maintains he was not in that bathroom when the shot was fired.

"I was a few blocks away, trying to get a tire fixed on my car," he said in a recent interview with The Associated Press at Brushy Mountain State Prison, where he is serving a 99-year sentence. "When I started back to my room I saw a police roadblock had been set up; it was about that time that I heard on my car radio King had been shot and the police were looking for a man in a white Mustang, the same kind of car I was driving, so I took off for Atlanta."

Ray, who had checked into the rooming house the day King was killed, said he was in Memphis to take part in an illicit gun-running scheme. He said the scheme was concocted by a mystery man named Raoul, an international smuggler whom Ray contends he met several months earlier at a waterfront bar in Montreal.

He also says Raoul, whom he describes as a blond man with a Latin American accent, set him up to be framed for King's murder.

"The fact is I don't know who killed King," said Ray, who recently turned 60. "I only pleaded guilty because I was desperate. I had been in isolation for eight months in the Memphis jail, and Percy Foreman was pressuring me to cop a plea. He was telling me my family would get in trouble and I'd get the death penalty if I didn't do what he said."

Foreman, the Houston attorney who represented Ray when he entered his guilty plea March 10, 1969, angrily disputes these assertions.

"The s.o.b. got down on his knees and thanked me for saving his life when I told him I had gotten the prosecutor to go along with a guilty plea," Foreman said when contacted in Houston recently.

Foreman, now in his mid-80s, says he thinks Ray was extremely fortunate not to have stood trial. He also rejects Ray's story about Raoul. "I think he acted alone," he said.

Asked what might have motivated Ray to commit such an act, Foreman said, "It was racism. His conversations simply steamed with racist remarks."

Ray, who was a fugitive from the Missouri State Penitentiary at the time King was killed, denies he harbored any ill will toward King and defies anyone to prove otherwise.

"King was just another politician to me," he said. "Why would I want to do something like kill a big-shot politician, me a fugitive, and bring all that heat down on myself?"

He admits buying the rifle, a Remington Gamemaster, 30.06 caliber, that authorities say was the murder weapon. But he says he bought it, at a Birmingham, Ala., gun shop, at Raoul's instruction and with money provided by Raoul.

"I gave the rifle to Raoul," Ray said. "If I had been buying it to kill King, you can bet I wouldn't have bought it at a gun shop. I would have gotten it from a fence, so it couldn't have been traced."

Birmingham lawyer Arthur Hanes Sr. said he tends to believe that story. He represented Ray for four months before Foreman.

"I've never believed Ray shot King," said Hanes, a former FBI agent and one-time Birmingham mayor. "I personally stood in that flophouse bathroom and looked across to the motel balcony where the Rev. King was standing when he was shot. It was a difficult angle. Ray simply didn't have enough expertise with rifles to make a shot like that, in my opinion."

Hanes also said he had never heard Ray utter a single racist statement.

"I've given this case a lot of thought, and I've concluded someone assisted Ray," he added, "but I can't say who."

The case should have gone to trial, he said, "to clear the air, if nothing else. I tried to get the judge to try the case, but he said there was too much pressure, from the government and the Memphis business community, to accept a guilty plea and avoid the publicity that a trial would generate."

The judge, W. Preston Battle, died a week after Ray's guilty plea. However, the chief prosecutor, Philip Canale, acknowledged last week that, contrary to Foreman's assertion, he had been happy to get a plea from Ray.

"It would have been a big, time-consuming and expensive trial with dozens and dozens of witnesses from all over the country," said Canale, now an assistant U.S. Attorney in Memphis. "I have never regretted the guilty plea because we got a substantial sentence. Also, I didn't want to take a chance on getting a cranky juror and having a mistrial."

Canale added that although he had no eyewitness and the evidence against Ray was largely circumstantial, he doesn't buy the conspiracy theory.

"I think he acted alone," he said, noting that the FBI had found Ray's fingerprint on the rifle discarded by the gunman near the scene of the crime.

However, supporters of Ray's story say his fingerprint was on the rifle because he had purchased it. They also note that, while Ray is a lifelong non-smoker, Viceroy cigarette butts were found in the rooming house bathroom and in his car ashtray, and that two sizes of clothing were found in his trunk.

Ray said the fact that Raoul often used his car may explain the butts in the ashtray and clothes in the trunk. "As for cigarettes in the bathroom I can't say because I was never in that bathroom," he said. "My prints were never found in there, you know."

After two years of hearings, ending in 1978, the House Select Committee on Assassinations couldn't answer that question. The committee issued a report saying Ray probably had been part of a larger conspiracy.

But while the committee couldn't say who else had participated in the plot, it did exonerate the CIA and FBI, both of which had conducted extensive illegal surveillance and smear campaigns against King throughout the 1960s. Former FBI Director J. Edgar Hoover was known to have hated King.