Lethal injection timeline

Many states once used a combination of three drugs to bring about death — sodium thiopental, to induce coma; pancuronium bromide, to induce paralysis; and potassium chloride, to stop the heart. But in 2011, the supply of sodium thiopental dried up, and Georgia began using one drug — pentobarbital — to anesthetize and then kill the condemned. Some key dates:

Dec. 7, 1982: Texas executes Charles Brooks Jr., the first inmate in the U.S. to die by lethal injection.

April 16, 2008: The U.S. Supreme Court finds that Kentucky's method of execution — a three-drug injection similar to that used in Georgia — does not violate the Constitution's ban on cruel and unusual punishment.

Jan. 12, 2011: Hospira, the sole U.S. manufacturer of sodium thiopental, says it will no longer produce the drug. Lundbeck, the Danish manufacturer of pentobarbital, acts to prevent sales of pentobarbital to any U.S. prison or corrections department. As many as 14 states, including Georgia, switch to a single-drug protocol — typically a large dose of pentobarbital. Georgia acquires its drug from an unidentified compounding pharmacy.

March 26, 2013: The Georgia General Assembly passes a bill that protects the identities of companies that provide execution drugs — making them a "state secret." House Bill 122 enables the state to keep secret even such information as a given drug's expiration date.

April 29, 2014: Oklahoma refuses to disclose the combination of drugs it intends to use in the execution of Clayton Lockett, in spite of lengthy litigation by Lockett's lawyers. Ten minutes after the injection of a sedative, a doctor pronounces the inmate unconscious and ready for the two drugs that will kill him. But Lockett isn't unconscious, and he thrashes and writhes in pain after the two drugs are administered. An official halts the execution, but Lockett dies of a heart attack 43 minutes after the execution began.

Jan. 23, 2015: The Supreme Court agrees to hear an Oklahoma case challenging the state's use of the three-drug combination. Oral arguments will be heard in April and the case decided by late June.

March 2, 2015: Execution of Kelly Gissendaner in Georgia is postponed at the last minute because the pentobarbital "appears cloudy," a corrections spokeswoman says. The next day, the state calls off Gissendaner's execution and that of another inmate, scheduled for next week, until it can evaluate its supply of pentobarbital.