The Florida Supreme Court rejected yet another appeal by Manuel Valle, slated to be executed tomorrow at 4 p.m.

Tuesday’s ruling is the third appeal by Valle’s lawyers rejected by courts this summer. His execution by lethal injection has twice been put on hold, first by the Florida Supreme Court and later by federal judges in Atlanta.

Valle’s lawyers have questioned the state’s use of a new drug in the lethal injection “cocktail.” The Department of Corrections has substituted the compound sodium pentobarbital for the first of the three-drug lethal injection protocol, a change forced by a manufacturer’s discontinuing of the drug formerly used.

British neurologist David Nicholl, who has ties to pentobarbital’s manufacturer Lundbeck Inc., filed the latest appeal with the state’s highest court, arguing that the use of the drug – also known as Nembutal – for executions violates the federal Controlled Substances Act which prohibits its dispensation except for legitimate medical purposes. The Court disagreed.

Since his conviction for the 1978 killing of Coral Gables police officer Louis Pena, Valle has been sentenced to death and re-sentenced three times in legal wrangling that eventually reached the U.S. Supreme Court, which overturned his death penalty in 1987. Courts later reaffirmed his death penalty conviction.

Valle has another appeal pending before the U.S. Supreme Court. His is the first – and only – death warrant signed by Gov. Rick Scott since he assumed office in January.

The Florida Supreme Court refused to grant a stay of execution for John Richard Marek, a convicted murderer scheduled to be put to death by lethal injection at 6 p.m. today.

Marek and Raymond Wigley were convicted of kidnapping, raping and murdering Adela Marie Simmons in 1983 when her car broke down on the turnpike near Stuart.

Marek has another appeal pending before the U.S. Supreme Court. A circuit court judge on Monday also denied another hearing to Marek, who claims that Wigley killed Simmons. Wigley was sentenced to life while Marek received the death penalty. Marek’s lawyers argue that he, too, should be serving life in prison.

Marek has spent more than two decades on Florida’s Death Row. Gov. Charlie Crist ordered him to be put to death in May but the Supreme Court halted that. If the execution takes place today, Marek will be the fourth Death Row inmate to be executed since Crist took office in 2007.