The man considered the father of lethal injection in the United States said it doesn't matter whether three fatal drugs are used or one — as his home state of Ohio has proposed — as long as the drug works efficiently.

Dr. Jay Chapman, who developed the lethal three-drug cocktail in the 1970s when he was the Oklahoma state medical examiner, said Ohio's decision to become the first state in the nation to use only one drug achieves that goal.

He said there was no particular reason he didn't propose a single drug, other than a concern that it might take a little longer to work. His three-drug method became widespread after states copied Oklahoma.

Now Chapman, semiretired in California at age 70, said he believes the system he helped create shows condemned inmates too much mercy.

"Their death is made much too easy by this sort of protocol for the crimes that they committed," he told The Associated Press last week.

But he said the hope was injection would avoid the pain-and-suffering arguments and allow executions to take place.

Under Ohio's new system, executioners would use a single large dose of thiopental sodium, an anesthetic, to put inmates to death, similar to the way veterinarians euthanize animals.