Utah, the only state in the past 40 years to carry out a death sentence by firing squad, is poised to bring back the executions if the state cannot find a supply of the drugs used in lethal injections. Here's a look at how some other states are dealing with the nationwide shortage:
The U.S. Supreme Court is poised to review Oklahoma's use of the sedative midazolam in executions, and state legislators are considering the use of nitrogen gas to kill death-row prisoners. The sponsor of the nitrogen bill says the gas would gradually deprive inmates of oxygen, resulting in a painless death.
The method has never been used in an execution in the United States. If the effort passes, nitrogen would be the state's first alternative to lethal injection. Electrocution would move to third and firing squads to fourth. The bill was prompted by the botched execution of an inmate last April. Clayton Lockett struggled against his restraints after attendants administered lethal drugs through a poorly placed intravenous line.
Since the state's last execution in 2005, inmates successfully argued in court that legislators ceded too much power over death row protocols to Arkansas' Correction Department. A subsequent lawsuit claims new protocols put inmates at risk of an agonizing death. In this year's legislative session, one lawmaker suggested abolishing the death penalty, but another lawmaker whose daughter was murdered in 1999 wants firing squads as another option for executioners.
Idaho allows prison officials to choose one of four options for lethal injection executions, depending on which chemicals are available. However, the state execution policy also gives both the Idaho Department of Correction director and the chief of prisons operations the power to change the execution procedure at any time, based on their own discretion.
Idaho law once allowed execution by firing squad, though the option was never used. It was removed from the books in 2009.
Last year, Idaho prison officials considered asking lawmakers to bring back the state's firing squad, but axed the plan after determining it would cost at least $300,000 to set up the squad.
The Wyoming Legislature has considered the use of firing squads in the past two legislative sessions. Republican state Sen. Bruce Burns, who introduced the bills, said he considers the gas chamber to violate the constitutional prohibition against cruel and unusual punishment and would opt for using the firing squad because it would be the cheapest option.
In the legislative session that wrapped up this month, the Wyoming House and Senate deadlocked over whether the state should offer to sedate inmates before shooting them. A majority of senators supported offering sedation while the House rejected the idea. The session ended before they could reach agreement. Officials with the state corrections department say they don't have drugs on hand that would allow them to carry out an execution if they needed to, although no one is on death row in the state.
In Tennessee, legal challenges to lethal injection and difficulty obtaining drugs have stalled planned executions for more than five years. Several death-row inmates have died in prison while awaiting execution.
Last year, the Tennessee Legislature attempted to jump-start the process by reinstating use of the electric chair. A new law allows inmates to be put to death by electrocution if the state is not able to obtain lethal injection drugs or if lethal injection is ruled to be unconstitutional.
But the law only brought a new legal challenge. Thirty-three death row inmates sued Tennessee over the constitutionality of both lethal injection and the electric chair. Several scheduled executions have been postponed in recent months to allow those challenges to be heard.
At a December hearing on one aspect of the lawsuit before the Tennessee Supreme Court, justices asked the inmates' attorney to name a method of execution that he did consider constitutional. The attorney, Steve Kissinger, at first tried to avoid the question. When pressed, he mentioned the firing squad and hanging.
Texas is almost out of the drug it uses to execute inmates. The state executed a Mexican mafia hit man Wednesday using its second-to-last dose of pentobarbital, leaving authorities with enough of the powerful sedative to carry out just one more execution. By far the nation's most active death penalty state, Texas has executed 522 inmates since 1982, when it became the first state to use lethal injection. The state is searching to replenish its pentobarbital supply.
Ohio executions are on hold as the state struggles to find supplies of lethal-injection drugs. After running out of its two previous drugs, the state switched to a never-tried two-drug combination of midazolam, a sedative, and hydromorphone, a painkiller.
In that method's only use, in January 2014, inmate Dennis McGuire repeatedly snorted and gasped during his 26-minute execution, the state's longest. Ohio postponed executions as lawsuits were filed over McGuire's death, and eventually the state dumped the two-drug combo last year.
Instead, the prisons department said it will use one of two drugs in future executions: pentobarbital or sodium thiopental. The catch is Ohio doesn't have either drug and both are virtually impossible to obtain except in specialty batches known as compounded drugs. The state has delayed all executions until 2016 and beyond.
After its supply of execution drug pentobarbital expired in March 2013, the state turned to a compounding pharmacy. The state has carried out four executions using compounded pentobarbital but hit a snag on March 2, when corrections officials postponed the scheduled execution of Kelly Renee Gissendaner because the lethal injection drug appeared cloudy.
Corrections officials announced the following day that they would postpone Gissendaner's execution and that of another inmate who was set for execution March 10 to give time to analyze the pentobarbital. Executions in the state are currently on hold while corrections officials carry out their investigation.
Five inmates on Pennsylvania's death row want a state court to throw out a plan to use a three-drug mixture to execute them. The Department of Corrections wants the court to throw out the lawsuit, which claims state officials did not have legal authority to establish the current procedures in 2012. If the court sides with the inmates, the case will continue and could result in a trial.
Pennsylvania has executed only three people since the death penalty was reinstated in 1976, the most recent in 1999.
Contributing to this story were Andrew Welsh-Huggins in Columbus, Ohio; Ben Neary in Cheyenne, Wyoming; Travis Loller in Nashville; Kate Brumback in Atlanta; Meg Kinnard in Columbia, South Carolina; Mark Scolforo in Harrisburg, Pennsylvania; Mike Graczyk in Houston.