The Supreme Court on Tuesday agreed to consider the constitutionality of lethal injections in a case that could affect the way inmates are executed around the country.

The high court will hear a challenge from two inmates on death row in Kentucky -- Ralph Baze and Thomas Clyde Bowling Jr. -- who sued Kentucky in 2004, claiming lethal injection amounts to cruel and unusual punishment.

Baze has been scheduled for execution Tuesday night, but the Kentucky Supreme Court halted the proceedings earlier this month.

The court has previously made it easier for death row inmates to contest the lethal injections used across the country for executions.

But until Tuesday, the justices had never agreed to consider the fundamental question of whether the mix of drugs used in Kentucky and elsewhere violates the Eighth Amendment's ban on cruel and unusual punishment.

Baze and Bowling say the procedure inflicts unnecessary pain and suffering on the inmate.

The two inmates sued in 2004 and a trial was held the following spring. A state judge upheld the use of lethal injection and the Kentucky Supreme Court affirmed that decision. The appeal taken up Tuesday stems from that decision.

"This is probably one of the most important cases in decades as it relates to the death penalty," said David Barron, the public defender who represents Baze and Bowling.

All 37 states that perform lethal injections use the same three-drug cocktail. The three drugs consist of an anesthetic, a muscle paralyzer, and a substance to stop the heart. Death penalty foes have argued that if the condemned is not given enough anesthetic, he can suffer excruciating pain without being able to cry out.

U.S. District Judge Aleta Trauger ruled last week that Tennessee's method of lethal injection is unconstitutional and ordered the state not to execute a death row inmate. The state is still deciding whether to appeal the judge's ruling, but agreed to stop a pending execution.

A ruling from California in the case of convicted killer Michael Morales resulted in the statewide suspension of executions.

States began using lethal injection in 1978 as an alternative to the historic methods of execution: electrocution, gassing, hanging and shooting. Since the death penalty resumed in 1977, 790 of 958 executions have been by injection.

Baze, 52, has been on Death Row for 14 years. He was sentenced for the 1992 shooting deaths of Powell County Sheriff Steve Bennett and Deputy Arthur Briscoe.

Bennett and Briscoe were serving warrants on Baze when he shot them. Baze has said the shootings were the result of a family dispute that got out of hand and resulted in the sheriff being called.