Oklahoma botches execution

Inside this Oklahoma prison a death row inmate died of a heart attack during a botched execution.

Clayton Lockett, who was only 38 years-old, experienced a vein failure which prevented the lethal injection of three drugs from being fully effective.

The execution was halted when it became obvious something had gone wrong and penetentiary workers blocked the view of the guerney.

(SOUNDBITE) (English) MEDIA WITNESSES, SAYING:

"At 6:39 he's still lifting his shoulders and head, off the gurney, grimacing. And appeared to be in distress."

(SOUNDBITE) (English) MEDIA WITNESSES, SAYING:

"So from 6:23, the execution started. 6:39 is when they closed the curtains on us. A 16-minute process to watch."

The failed execution is likely to raise more questions about the lethal injection and whether it is humane.

Lockett was sentenced to death here for shooting and eventually killing a woman by burying her alive.

The execution of fellow inmate Charl