An anesthesiologist testified Monday that Ohio's lethal injection procedure isn't appropriate for dogs or cats, let alone humans.

Dr. Mark Heath's testimony on behalf of two murder defendants came in a Lorain County hearing on the constitutionality of state's method for putting prisoners to death.

Heath, an assistant professor of anesthesiology at Columbia University, says it's possible to perform lethal injection of prisoners in a humane manner, but that Ohio's method falls below the standard for euthanizing household pets.

Ohio requires its executions to be carried out "in a professional, humane, sensitive and dignified manner." The two men facing murder charges say the state's lethal injection procedure doesn't give the quick and painless deaths required by state law.

Lethal injections are on hold nationally while the U.S. Supreme Court considers a challenge in a case from Kentucky, which is among the roughly three dozen states that administer three drugs in succession to sedate, paralyze and kill prisoners.