By Bill Cotterell

TALLAHASSEE, Florida (Reuters) - The Florida Supreme Court overturned the conviction of a man on Death Row for 28 years for the abduction, rape and murder of a filling station attendant, ordering that he be given a new trial after doubts were raised about scientific evidence in the case.

Roy Swafford, 66, came within a few hours of execution in 1990 before a court-ordered stay kept him from Florida's electric chair. Thursday's ruling vacated his rape and murder convictions and his death sentence.

Swafford's attorney, Terri Backhus, said the state has 15 days to ask the Supreme Court for a rehearing before the case is sent back to the 7th Circuit in Daytona Beach. Prosecutors in Volusia county will then have to decide whether or not to go ahead with a new trial.

"The case was weak to start with. It was highly circumstantial," said Backhus. "The Supreme Court decision was pretty explicit. You can see how troubled they were with the evidence."

Backhus could seek a bond hearing while he awaits trial but she said Swafford faced other legal issues, including an escape conviction that would likely keep him in jail for the time being.

The high court, in a 5-2 decision, accepted Swafford's argument that newly discovered evidence, indicating no seminal fluid was found in the victim's body, created doubt that he was the killer. The court also agreed with his evidence disputing how a pistol used in the murder was linked to him.

Evidence indicated that acid phosphatase, a substance usually found in seminal fluid, was found but no sperm or semen could be confirmed in laboratory results from Florida Department of Law Enforcement tests. The two justices, who voted to uphold Swafford's sentence, said a 2004 re-test of the 1982 swabs was unreliable.

"The acid phosphatase evidence was the linchpin of the state's case that a sexual battery occurred," said the court majority.

Swafford was sentenced to death in 1985 for the murder of Brenda Rucker on February 14, 1982. Swafford and some friends had driven from Nashville to Daytona Beach for the Daytona 500 race weekend. Trial testimony indicated Swafford was seen near a filling station where Rucker worked and that he disposed of a pistol in a bathroom trash can at a topless bar.

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The gun was found to be the murder weapon, but the court said there was insufficient evidence to prove Swafford had disposed of it.

Rucker was shot nine times and left in a wooded area, fully clothed. The high court said that, even without the disputed fluid evidence, "Swafford had a very limited time in which to kidnap the victim, take her to a different location and sexually batter her, redress her, kill her and then move the body to the location where the body was found."

The court said Rucker was seen at the filling station where she worked at about 6:18 a.m. and that Swafford returned at sunrise, about 45 minutes later, to a camp site where he and four Nashville friends were spending the weekend.

The justices also said another man, Michael Walsh, was a potential suspect, but information about him was not used in Swafford's trial.

It said Walsh had a car that resembled one seen at the filling station where Rucker was abducted and that he was later seen with a gun similar to the one used in the crime. The court said information about Walsh could be used in a retrial of Swafford, if prosecutors pursue the case.

(Editing by L Gevirtz)