Warner’s autopsy report revealed that potassium acetate, rather than the potassium chloride which Oklahoma’s protocol calls for, was used in his execution. Warner’s execution had previously been stayed when another inmate’s execution was botched on the day Warner had been scheduled for execution. Governor Mary Fallin recently put a hold on all executions in the state while reviewing the lethal injection protocol.

http://www.npr.org/sections/thetwo-way/2015/10/08/446862121/oklahoma-used-the-wrong-drug-to-execute-charles-warner