Wilmington, Del. ? A federal judge in Wilmington on Tuesday halted the execution of a convicted ax murderer until the Supreme Court rules on a challenge filed by a Florida inmate who claims lethal injection is unconstitutional.

U.S. District Judge Sue Robinson issued the injunction in the case of Robert W. Jackson III, who had been scheduled to die next week in Delaware.

In documents filed Monday, Jackson claimed the chemicals used in lethal injections could subject him to pain and suffering in violation of the Eighth Amendment.

Similar claims were made by Florida inmate Charles Hill, whose execution was blocked by the high court in January at the last minute, as Hill lay on a gurney with IV lines in his arms.

The justices are expected to issue a decision before July that will determine whether death-row inmates can file last-minute civil rights challenges claiming their deaths would be cruel and unusual punishment.