Updated

The Oklahoma Supreme Court has stayed the execution of two death row inmates who have challenged the state's secrecy protocol surrounding the source of lethal injection drugs.

In a 5-4 decision, the high court issued the stay Monday, just one day before death row inmate Clayton Lockett was scheduled to be executed for the 1999 shooting death of 19-year-old Stephanie Nieman.

The second inmate, Charles Warner, was convicted in the 1997 death of his roommate's 11-month-old daughter. He was scheduled to die on April 29.

Oklahoma County District Judge Patricia Parrish last month struck down the state's execution law in a ruling that said the protocol that prevented the inmates from seeking information about the drugs used in lethal injections violated their rights under the state constitution.