OKLAHOMA CITY (AP) — Oklahoma had conducted 112 executions from 1976 to October 2015, when the state imposed a moratorium following three consecutive flawed executions or attempted executions. Here is a look at those and other issues surrounding capital punishment in Oklahoma as the state prepares to resume lethal injections.

— April 29, 2014: Clayton Lockett writhed and groaned on the gurney as Oklahoma used the surgical sedative midazolam for the first time during an execution. Then-state prisons director Robert Patton halted the execution process, but Lockett died 43 minutes later. The state later says an improperly placed intravenous line — not the new drug mix — caused problems with Lockett's execution. A second execution set that night, for Charles Warner, was postponed.

— June 25, 2014: Inmates sue Oklahoma, alleging the state unconstitutionally allows an "ever-changing array of untried drugs" during executions.

— Dec. 22, 2014: A federal judge declares Oklahoma's lethal injection protocol constitutional. The U.S. Supreme Court says later it will consider whether Oklahoma can use midazolam during executions, but it doesn't disrupt Warner's rescheduled execution.

— Jan. 15, 2015: Oklahoma executes Warner for the 1997 killing of his roommate's infant daughter. "My body is on fire," he said after receiving midazolam, though he showed no other signs of distress.

— April 18, 2015: Gov. Mary Fallin signs a bill into law making Oklahoma the first state in the nation to approve the use of nitrogen gas for executions.

— June 29, 2015: A sharply divided U.S. Supreme Court upholds Oklahoma's use of midazolam during executions.

— Sept. 30, 2015: Prison officials prepare to execute Richard Glossip, but Oklahoma Gov. Mary Fallin issues a 37-day stay, saying the state Department of Corrections received the wrong drug, potassium acetate, rather than the potassium chloride listed in the state's execution protocol.

— Oct. 2, 2015: All executions are put on indefinite hold in the state by the Oklahoma Court of Criminal Appeals at the request of Attorney General Scott Pruitt, who calls for an inquiry into the state's execution procedures.

— Oct. 8, 2015: The Oklahoman newspaper reports that the state used potassium acetate during Warner's execution in January, rather than potassium chloride. Fallin says she agrees all executions should be delayed after an autopsy report revealed the wrong drug was used to stop the inmate's heart.

— May 19, 2016: An Oklahoma grand jury investigating the state's execution procedures issues its 106-page report with no indictments.

— April 25, 2017: A bipartisan commissio n co-chaired by former Gov. Brad Henry recommends extending a moratorium on executions until major changes are made to the state’s capital punishment system.

— March 18, 2018: Oklahoma officials announced plans to develop protocols to use nitrogen gas to execute inmates.

—Feb. 13, 2020: Oklahoma officials announce plans to resume executions by using a three-drug lethal injection protocol.