Last summer, attorneys for a group of five Arkansas death-row inmates asked a U.S. District judge to force Nebraska to provide them information about where it got the fentanyl it ultimately used in Carey Dean Moore's execution in August.

They argued it was relevant to a pending lawsuit in federal court in Arkansas where they were challenging, among other things, the state's use of midazolam in executions, which they called inhumane.

Little Rock attorney John Williams contended a protocol that uses diazepam and fentanyl would "significantly reduce the substantial risk of pain and suffering inherent in the midazolam protocol," and pointed to Nevada and Nebraska, which both obtained the drugs for executions.

In a brief, he argued information Nebraska has about its source was necessary to determine whether the drug could be made available to Arkansas for use in executions, a required element of the inmates' claim.

At stake, attorneys say, is the right of at least 17 men to not be subjected to cruel and unusual punishment during their executions.

When the prison and the Nebraska Attorney General's office refused to provide it, they sought an order compelling them to comply under a subpoena issued in the Eastern District of Arkansas.