Three death row inmates are suing the Texas prison system to challenge what they contend is use of untested drugs in future executions.
One of the plaintiffs in the suit filed Tuesday in Houston federal court is Michael Yowell. He faces lethal injection next week in Huntsville for killing his parents at their home in Lubbock.
The lawsuit filed on the inmates' behalf is demanding Texas Department of Criminal Justice officials fully disclose the drugs they're using and their source so the condemned prisoners won't endure pain and suffering.
Texas' previous supply of pentobarbital, the drug it uses for executions, expired last month. And like other death penalty states, Texas has had difficulty obtaining new drug supplies for capital punishment use.
Corrections officials say they haven't seen the lawsuit.