Death penalty timeline
April 29 – Clayton Darrell Lockett, 38, is executed. The execution was halted after a supposedly unconscious Lockett began speaking and writhing on the table. He died of a heart attack 43 minutes after the execution began. Charles Frederick Warner was set to be executed as well, but it was not carried out following the Lockett debacle.
Sept. 30 – After months of investigation and review, DOC releases its revised execution protocol. The protocol mirrors that of Arizona, where Director Robert Patton formerly worked.
Oct. 10 – DOC officials show off the renovated execution chamber at the Oklahoma State Penitentiary. More than $106,000 was spent on the renovation, most of which was spent updating the operations room and death chamber itself. So far it has been used only once.

Jan. 15 – Charles Frederick Warner, 47, is executed. It is later learned that a wrong drug — potassium acetate rather than potassium chloride — was used in his execution.
April 14 – Nitrogen gas inhalation adopted by state Legislature as execution option.
Sept. 16 – The Oklahoma Court of Criminal Appeals stays the execution of Richard Glossip mere hours before he was scheduled to die by lethal injection. A new execution date is set for Sept. 30.
Sept. 30 – DOC officials realize they have again purchased potassium acetate instead potassium chloride as they prepare to execute Richard Glossip later that day. Glossip’s execution was halted.
Oct. 2 – Oklahoma Court of Criminal Appeals imposes indefinite stay on all executions.

Nov. 8 – Despite state’s recent problems conducting executions, not to mention the court-mandated stay, Oklahoma voters elect to enshrine executions in the state’s constitution. The vote ensures capital punishment will be available even if higher courts later rule lethal injection unconstitutional.

March 14 – Department of Corrections Director Joe Allbaugh announces DOC will use nitrogen gas as primary method of execution.

March 13 – Oklahoma Attorney General Mike Hunter tells television station KFOR that the delay in finishing the state’s new death penalty protocol is due to difficulties in finding a device that will administer nitrogen gas, saying that manufacturers of such devices are wary of public blowback.

March 28 – Hunter tells attendees at an Oklahoma District Attorneys Council meeting that, unable to purchase the equipment needed to administer nitrogen in an execution, the state would instead look to build its own device.