CHICAGO (AP) — The image of gunmen in a row firing in unison at a condemned prisoner may conjure up a bygone, less enlightened era.

But the idea of using firing squads is making a comeback. Idaho lawmakers passed a bill this week seeking to add the state to the list of those authorizing firing squads, which currently includes Mississippi, Utah, Oklahoma and South Carolina.

Fresh interest comes as states scramble for alternatives to lethal injections after pharmaceutical companies barred the use of their drugs.

Some, including a few Supreme Court justices, view firing squads as less cruel than lethal injections, despite the violence involved in riddling bodies with bullets. Others say it’s not so cut-and-dry, or that there are other factors to consider.

A look at the status of firing squads in the United States:

WHEN WAS THE LAST EXECUTION BY FIRING SQUAD?

Ronnie Lee Gardner was executed at Utah State Prison on June 18, 2010, for killing an attorney during a courthouse escape attempt.

Gardner sat in a chair, sandbags around him and a target pinned over his heart. Five prison staffers drawn from a pool of volunteers fired from 25 feet (about 8 meters) away with .30-caliber rifles. Gardner was pronounced dead two minutes later.

A blank cartridge was loaded into one rifle without anyone knowing which. That’s partly done to enable those bothered later by their participation to believe they may not have fired a fatal bullet.

Utah is the only state to have used firing squads in the past 50 years, according to the Washington, D.C.-based Death Penalty Information Center.

WHAT HAS CAUSED THE LETHAL DRUG SCARCITY?

Under Idaho’s bill, firing squads would be used only if executioners can’t obtain the drugs required for lethal injections.

As lethal injection became the primary execution method in the 2000s, drug companies began barring use of their drugs, saying they were meant to save lives, not take them.

States have found it difficult to obtain the cocktail of drugs they long relied on, such as sodium thiopental, pancuronium bromide and potassium chloride. Some have switched to more accessible drugs such as pentobarbital or midazolam, both of which, critics say, can cause excruciating pain.

Other states have reauthorized the use of electric chairs and gas chambers — or are at least considering doing so. That’s where firing squads come in.

ARE THEY MORE HUMANE?

Supreme Court Justice Sonia Sotomayor is among those who say firing squads are a more humane method of execution.

That idea is based on expectations that bullets will strike the heart, rupturing it and causing immediate unconsciousness as the inmate quickly bleeds to death.

“In addition to being near instant, death by shooting may also be comparatively painless,” Sotomayor wrote in a 2017 dissent.

Her comments came in the case of an Alabama inmate who asked to be executed by firing squad. A Supreme Court majority refused to hear his appeal. In her dissent, Sotomayor said lethal drugs can mask intense pain by paralyzing inmates while they are still sentient.

“What cruel irony that the method that appears most humane may turn out to be our most cruel experiment yet,” she wrote.

BUT IS DEATH BY FIRING SQUAD REALLY PAINLESS?

In a 2019 federal case, prosecutors submitted statements from anesthesiologist Joseph Antognini, who said painless deaths by firing squads are not guaranteed.

Inmates could remain conscious for up to 10 seconds after being shot depending on where bullets strike, Antognini said, and those seconds could be “severely painful, especially related to shattering of bone and damage to the spinal cord.”

Others note that killings by firing squad are visibly violent and bloody compared with lethal injections, potentially traumatizing victims’ relatives and other witnesses as well as executioners and staffers who clean up afterward.

ARE FIRING SQUADS MORE RELIABLE?

If reliability means the condemned are more likely to die as intended, then one could make that argument.

An Amherst College political science and law professor, Austin Sarat, studied 8,776 executions in the U.S. between 1890 and 2010 and found that 276 of them were botched, or 3.15%.

The executions that went wrong included 7.12% of all lethal injections — in one notorious 2014 case in Oklahoma, Clayton Locket writhed and clenched his teeth after midazolam was administered — as well as 3.12% of hangings and 1.92% of electrocutions.

By contrast, not a single one of the 34 firing squad executions was found to have been botched, according to Sarat, who has called for an end to capital punishment.

The Death Penalty Information Center, however, has identified at least one firing squad execution that reportedly went awry: In 1879, in Utah territory, riflemen missed Wallace Wilkerson’s heart and it took 27 minutes for him to die.

WERE FIRING SQUADS EVER IN WIDE USE?

Firing squads have never been a predominant method of carrying out civilian death sentences and are more closely associated with the military, including the execution of Civil War deserters.

From colonial days through 2002, more than 15,000 people were put to death, according to data compiled by death penalty researchers M. Watt Espy and John Ortiz Smykla. Just 143 died by firing squad, compared with 9,322 by hanging and 4,426 by electrocution.

HAS THE SUPREME COURT WEIGHED IN?

High court rulings have required inmates who oppose an existing execution method to offer an alternative. They must prove both that the alternative is “significantly” less painful and that the infrastructure exists to implement the alternative method.

That has led to the spectacle of inmate attorneys bringing multiple cases in which they argue the merits of firing squads.

In 2019, the Supreme Court ruled in Bucklew v. Precythe that some pain does not automatically mean a method of execution constitutes “cruel and unusual” punishment, which is prohibited by the Eighth Amendment.

The Constitution “does not guarantee a prisoner a painless death — something that, of course, isn’t guaranteed to many people,” Justice Neil Gorsuch wrote for the 5-4 majority.

Key factors in deciding whether a method is “cruel and unusual” include whether it adds extra pain “beyond what’s needed to effectuate a death sentence,” Gorsuch said.

___ Follow Michael Tarm on Twitter at @mtarm.