The botched execution of an Oklahoma inmate is certain to fire up the long-running debate over what constitutes cruel and unusual punishment.

In Oklahoma, 38-year-old Clayton Lockett began writhing, clenching his teeth and straining to lift his head off the pillow Tuesday evening after he was supposedly rendered unconscious by the first of three drugs in the state's new lethal injection combination.

The execution was halted, and authorities said Lockett died of a heart attack about a half-hour later.