Mark D. Schwab, who was convicted of raping and killing a child, was put to death Tuesday at Florida State Prison. Thus, he became the first prisoner to be executed since a mishandled lethal injection 18 months ago raised concern that a condemned man had suffered a "cruel and unusual" ordeal.

Schwab, 39, was executed for the rape and murder of 11-year-old Junny Rios-Martinez of Cocoa. He killed the boy in April 1991, just a month before he had been freed early from a prior prison term for sexually assaulting a 13-year-old boy.

Schwab’s death occurred at 6:15 p.m. EDT, according to Erin Isaac, representative for Florida Gov. Charlie Crist.

Schwab’s lawyers made an unsuccessful appeal to the U.S. Supreme Court late Monday, arguing that the last execution at the prison near Starke, in December 2006, was botched, causing extreme and extended pain on 55-year-old Angel Nieves Diaz.

"Florida is a state with a long history of failed and disconcerting executions," Schwab's appeal said, referring to gruesome incidents in the 1990s when the state's electric chair, nicknamed Old Sparky, set fire to the heads of condemned men before they died.

In the Diaz case, executioners missed the convict's vein and injected chemicals into muscle tissue. Immediately after that, Gov. Jeb Bush decreed a moratorium on executions and ordered a review of lethal-injection procedures.

The state Department of Corrections made average changes based on the review panel's recommendations but maintained the three-drug method used since Florida switched from executions by electric chair to lethal injection eight years ago.

Death penalty opposers argue that the drugs are poorly understood by those who administer them and that they can cause pain, in violation of the constitutional prohibition against cruel and unusual punishment.