Lawyers for the five prisoners argued to the 5th U.S. Circuit Court of Appeals that an agreement between the Texas Department of Criminal Justice and two other inmates to test the pentobarbital for their lethal injections should be extended to them. They say failure to do so would violate their constitutional right to equal protection under the law.
The appeals court on Monday upheld a Houston federal judge's dismissal of the lawsuit.
It also said no risk of failure has been shown in the state's use of the sedative pentobarbital for executions.