Glossip was the plaintiff in Glossip v. Gross, a U.S. Supreme Court case decided in June 2015 in which a divided Court ruled 5-4 that midazolam may be used as a sedative in combination with other lethal injection drugs. The case was originally titled Warner v. Gross, but Glossip replaced Charles Frederick Warner as the plaintiff after Warner was executed in January 2015, also by Oklahoma, before the case was decided.