Updated

A federal appeals court on Saturday granted an Arizona death row inmate's request to postpone his pending execution, putting it on hold until prison officials reveal details on the two-drug combination that will be used to put him to death.

The preliminary injunction granted by the 9th U.S. Circuit Court of Appeals reversing a lower federal court comes four days before the scheduled execution of Joseph Rudolph Wood.

Without weighing in on the "ultimate merits" of Wood's case, the court wrote: "Wood has presented serious questions going to the merits of his claim, and that the balance of hardships tips sharply in his favor."

Wood's lawyers argued prison officials violated their client's First Amendment rights by refusing to provide the detailed information, such as the makers of the drugs and how the state developed its method for lethal injections.

"Today the Court has made a well-reasoned ruling affirming the core First Amendment principles regarding the public's right to know, which aid all parts of our democratic government," Wood's lawyer Dale Baich said in a statement.

Attorneys for the state argued there was no First Amendment right to the information Wood is seeking. Phone and email messages seeking comment from the attorney general's office were not immediately returned.

The arguments by Wood's attorneys are an example of a new legal tactic in death penalty cases, which emerged as states face problems getting supplies of lethal-injection drugs.

In the past, states used the same three-drug combination and didn't have problems getting access to the drugs, until the maker of a sedative used in executions decided not to make it anymore. Then, states started to shield the identity of the drugmakers.

The legal dispute in Arizona is emerging as concerns over the death penalty mount after a botched April 29 execution of an Oklahoma inmate and an incident in January in which an Ohio inmate snorted and gasped during the 26 minutes it took him to die.

Arizona prison officials intend to use the same drugs -- the sedative midazolam and painkiller hydromorphone -- used in the Ohio execution. A different drug combination was used in the Oklahoma case.

Wood, 55, had been scheduled to be executed Wednesday in the August 1989 shooting deaths of his estranged girlfriend, Debra Dietz, and her father, Eugene Dietz, at an automotive shop in Tucson.