Hill, who had originally been due to be put to death on Tuesday with a lethal injection, won an 11th hour delay after his lawyers petitioned the Supreme Court arguing that his death would be cruel and inhumane under the US constitution.
A single Supreme Court justice temporarily halted Tuesday's execution and this was confirmed by the full court on Wednesday so that it could review the case.
Hill's lawyers based their argument on the combination of lethal chemicals to be used by the southern state in the execution.
Hill, 47, was condemned to death for the murder of a Florida policeman in 1982.
Hill was already attached to intravenous tubes to deliver a deadly cocktail when Supreme Court justice Anthony Kennedy issued a temporary stay.
Hill was about an hour from receiving a deadly injection of sodium pentothal, an anaesthetic, pancuronium bromide and potassium chloride.
Witnesses had gathered for the execution at the Florida State Prison and Hill had already been attached to intravenous tubes to receive the cocktail, his lawyers said.
The lawyers cited a recent medical study that said pancuronium bromide causes suffocation while potassium chloride causes burning in the veins and massive muscle cramping before cardiac arrest.
The Supreme Court judges will not directly consider whether the method used by Florida is illegal. They will decide whether Hill can make the claim of "inhumane" treatment using a federal civil rights law.