A group of US-based media outlets on Thursday launched a legal bid to obtain information about drugs due to be used in a lethal injection in Missouri next week following a botched execution in Oklahoma.
Convicted murderer Russell Bucklew is scheduled to be executed on May 21 by Missouri, one of several death penalty states which refuses to disclose the origin of drugs it uses in lethal injections.
The 32 states which practice the death penalty have faced a crisis ever since the European manufacturers of the most commonly used lethal injection drugs ceased supplying them.
States have increasingly turned to compounding pharmacies outside US federal regulation to provide drugs for execution, despite criticism that the drugs can cause excruciating pain to those being put to death.
A 26-page legal filing lodged by the media outlets said information about executions had historically been made available to the public under the US Constitution.
"The constitution thus compels access to historically available information about the type and source of drugs used in lethal injection executions because disclosure promotes the functioning of the process itself and is essential for democracy to function," said the filing, signed by Bernard Rhodes and David Schultz, representing the five media outlets.
The legal action has been taken up by The Associated Press news agency, the US office of Britain's The Guardian, and the Kansas City Star, The St Louis Post-Dispatch and the Springfield News-Leader.
Controversy over the drugs used in lethal injections has swirled since April 29, when convicted killer Clayton Lockett took 43 minutes to die, appearing to writhe in agony, after his lethal injection.
If Bucklew's lethal injection goes ahead as scheduled, it will be the first in the United States since Lockett's execution.