JACKSONVILLE, Fla. -- The U.S. Supreme Court asked Florida to delay the Wednesday execution of an inmate just 15 minutes before he was scheduled to be executed.

Johnny Robinson (pictured, left) asked the federal courts to stop his execution for the 1985 abduction, rape and murder of a Plant City woman, saying the state's procedures for execution and sentencing are unconstitutional.

After reviewing the convicted killer's file, Gov. Jeb Bush said he had no second thoughts about the scheduled execution. But the Supreme Court called Bush's office and asked them to wait for further word.

Robinson, 51, filed appeals late Monday with the U.S. Supreme Court and U.S. District Court in Jacksonville, hoping to stop his execution for the murder of Beverly St. George, said Peter Cannon, Robinson's attorney.

In Jacksonville, a group of protestors peacefully demonstrated their opposition to the death penalty, appearing before the Duval County courthouse with signs reading "Time-out on executions." They argued that any killing is wrong, no matter who does it, and they urged Gov. Bush to hold off on any executions and review the constitutionality of the death penalty.

Inside the Duval County court, Robinson's attorneys are challenging Florida's use of lethal injection as cruel and unusual punishment, based on the use of pancuronium bromide. The drug paralyzes muscles, including the diaphragm, and is one of three used.

Opponents of the drug's usage say it can cause prisoners to suffocate before they lose consciousness and is so cruel that some states have banned its use by veterinarians to euthanize animals.

Deborah Denno, a professor of law at Fordham Law School, an expert on execution methods, said the "only purpose for pancuronium bromide is to keep someone still."

Denno said Texas, the first state to adopt lethal injection, used the three-chemical combination and 29 other states simply followed suit.

Cannon said it was the first attempt to use the argument in Florida, although the high court has rejected it in appeals from inmates in other states.

Florida Executions Florida has put 55 men and 2 women to death since the death penalty was reinstated in 1976.

In Washington, Robinson's appeal asks the Supreme Court to stop his execution based on an Arizona case known as the Ring decision. In that case, the high court ruled that the ultimate decision on the death penalty should rest with juries and not judges. In Florida, juries make a sentencing recommendation to the judge, who can either follow or reject their recommendation.

Several Florida inmates have been unsuccessful when attempting to use the Ring decision to spare their lives.

Carolyn Snurkowski, a death appeals lawyer in the Attorney General's Office, said her office had filed answers to both appeals, claiming the arguments should be thrown out because they should have been filed earlier.

St. George was traveling from Plant City to Virginia in August 1985 when her car broke down on Interstate 95 in St. Johns County. Robinson and a 16-year-old friend Clinton Fields drove up, took her prisoner at gunpoint, handcuffed her and took her back to his car.

She was raped, then shot twice in the head. Her body was found in a cemetery near St. Augustine the next day.

Five days after St. George's murder, Robinson was arrested for robbing four other people in a disabled car and raping one of them.

"He claims that the first shot was accidental," St. Johns County Sheriff Neil Perry said. "If it was accidental, he should have helped her, but he didn't. He then shot her a second time in the head to make sure she was dead because he didn't want her to testify against him."

Robinson was still on parole for a Maryland rape at the time. The handgun used to kill St. George was stolen in a burglary the week before.

In arguments rejected by the Florida Supreme Court, Robinson's lawyer had claimed that his client's murder conviction and death sentence were based on the recanted testimony of Clinton, who is mentally retarded with an IQ of 50. Clinton, who is serving a life sentence for St. George's murder, now says he never saw Robinson fire the fatal shots.

The state high court ruled Thursday that the trial judge looked at all the facts and determined that Fields' new story wasn't credible.

Robinson had already had his final meal when the stay of execution was handed down. He also spent four hours with a Jacksonville priest Wednesday. His family hasn't visited him since December 2003, when the death warrant was signed.