Arkansas uses a three-drug protocol in its lethal injection procedures. The first drug, midazolam, is meant to render the inmate comatose. The second drug, pancuronium bromide, will cause paralysis and stop breathing. And the third, potassium chloride — which the state only acquired on March 8 — stops the heart.

Experts, however, point out that midazolam, the drug set to expire on April 30, has sometimes failed to effectively knock out subjects.

Medically, the drug’s core function is an anti-anxiety sedative, not an anesthetic or execution device.

Death penalty experts say that increases the risk that the procedure could be rendered inhumane — and even constitute unlawfully cruel punishment.

“If the prisoner is placed under surgical anesthesia by the first drug, then the fact that the other two drugs cause pain wouldn’t matter,” explained Megan McCracken, a lethal injection expert at the University of California Berkeley School of Law’s Death Penalty Clinic. “But if that first drug for any number of reasons doesn’t work, then you have a person who is paralyzed who has been administered an incredibly painful drug that will cause cardiac arrest.”