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

Dr. Mark Heath, an assistant professor of anesthesiology at Columbia University, made the remarks Monday in Ohio while testifying on behalf of two murder defendants. The hearing is on the constitutionality of the state's method for putting prisoners to death.

Heath 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.

The major criticism of the three-drug execution is that if the executioner administers too little anesthetic or makes mistakes injecting it, the inmate could suffer excruciating pain from the other two drugs.

Lethal injections are on hold nationally while the U.S. Supreme Court considers a challenge in a case from Kentucky.