On a cool June night in 2010, Utah prison guards strapped convicted murderer Ronnie Lee Gardner into a heavy steel chair flanked by black sandbags, securing his head in a halo brace. A doctor put a stethoscope to Gardner's chest, then fastened a small target over the condemned man's heart.

Minutes later, five marksmen, identities unknown, trained their Winchester rifles on Gardner from 25 yards, then opened fire on the executioner's command. The fusillade exploded through the hooded inmate's torso, killing him almost instantly.

Gardner was the most recent U.S. prisoner to die by firing squad, a method of death once considered too brutal and offensive for civilized American society. But he might not be the last.

An ongoing shortage of lethal injection drugs – coupled with the grisly spectacle of botched executions and a number of legal challenges to the use of less-effective substitute drugs – has several states, and at least one inmate, calling for the return of the firing squad.

In 2015, Utah Gov. Gary Herbert, a Republican, signed a bill that established firing squads as an execution option, reversing an 11-year ban, though no one has been put to death since Gardner. In Mississippi, a bill authorizing firing squads cleared the state House in early February before the state Senate shot it down. Firing squads are on the books in Oklahoma, and lawmakers in other Southern states are said to be considering similar legislation.

Meanwhile, in late February, the U.S. Supreme Court denied the request by Thomas Arthur, an Alabama death-row prisoner who wanted the state to fatally shoot him rather than subject him to the likelihood of a painful death from secret, experimental lethal-injection drugs.

But Supreme Court Justice Sonia Sotomayor excoriated her colleagues for tacitly endorsing execution methods that could reasonably be considered as cruel or inhumane – and she pointed to firing squads as the way to go.

"Some might find this choice regressive, but the available evidence suggests that a competently performed shooting may cause nearly instant death," Sotomayor wrote in a blistering dissent. "In addition to being near instant, death by shooting may also be comparatively painless. And historically, the firing squad has yielded significantly fewer botched executions."

Death penalty opponents, however, say firing squads aren't fail-safe, the condemned don't always die immediately and the procedure smacks of tin-horn dictatorships, undermining America's global standing as a champion of human rights. That states are looking to salvage the practice, they say, is yet another sign that capital punishment is on its way out.

"I think that the death penalty is in big trouble in the United States," says Austin Sarat, an associate dean and law and political science professor at Amherst College.

"The legitimacy of capital punishment has been sustained in part by the belief that we could find a way of execution that would be safe, reliable and sane," says Sarat, the author of " Gruesome Spectacles: Botched Executions and America's Death Penalty ." He notes the same arguments officials are making for the firing squad – it's quick, it's humane, it's reliable – were the same ones proponents used for lethal injections as its more clinical, civilized replacement.

"It's a back-to-the-future [method] that was replaced for a reason," Sarat says.

The discussion over firing squads, however, has emerged against a series of bungled lethal-injection execution attempts, the effect of an engineered shortage of highly-effective drugs used to sedate and quickly kill the condemned.

Several years ago, in a blow against capital punishment, the worldwide pharmaceutical industry has stopped supplying the drug protocol to death-penalty states that execute by lethal injection. Because of the boycott – and several high-profile DNA exonerations of death-row inmates – the number of executions in the United States stalled, and then dropped to historic lows.

Scrambling for a Plan B, authorities began using combinations of drugs available on the market that were supposed to bring swift, painless death, but the opposite has happened.

Some inmates have remained conscious for several minutes, screaming in agony as the toxic chemicals entered their bloodstreams. Others have foamed at the mouth in violent spasms, gasping for air as they died. Experts say the experience is probably akin to being burned alive from the inside out; in one Oklahoma execution, inmate Clayton Lockett contorted in pain for nearly an hour before he died.

The firing squad execution chamber at the Utah State Prison after Ronnie Lee Gardner was executed in June of 2010 (Trent Nelson/Pool/AP)

Several death-row inmates have challenged the new drug combination as cruel and inhumane, but the Supreme Court ruled in 2015 that that the lethal cocktail was legal under the Constitution. Nevertheless, corrections officials and death-penalty opponents, eager to avoid macabre headlines, are resurrecting an anachronistic punishment once considered the stuff of pulp fiction and lawless banana republics.

"The elusive search in the modern era for humane methods of execution was a reaction to the perceived barbarity of death by methods like the firing squad," Phyllis Goldfarb, a George Washington University law professor, writes in an email.

"Death by firing squad is not pain- and botch-free," Goldfarb writes, noting some marksmen have missed the heart target and hit other parts of the body, while others have fired prematurely. "The condemned dies from blood loss and loses consciousness when blood supplied to the brain drops precipitously. Even when the people in the firing squad hit their target as intended, it may take at least a couple of minutes for the condemned to die and sometimes much longer."

To that point, firing-squad proponents have a quick retort: So what?

"How could a civilized society place a man before a firing squad, [opponents] ask," writes Joseph R. Murray II, a guest columnist for the Jackson, Miss., Clarion Ledger, commenting on the debate over the state's proposal to have inmates die by the bullet.

"To these folks, that's third-world justice. But isn't a firing squad the most humane way to execute a criminal? Isn't death instantaneous?" Murray asks. "Where lethal injection could go awry, causing prolonged pain, and electrocution could not work effectively, there is no doubt multiple bullets do the job quickly and safely."

Such was the case with Gardner, the Utah inmate who was executed in 2010. He was condemned for killing a bartender, then gunning down a lawyer in a brazen courthouse escape attempt in the 1980s. Though the state had outlawed firing squads six years before his execution, Gardner -- who had been behind bars for most of his adult life -- was an exception: Since he was sentenced in 1985, he got to choose his method of death.

"'I lived by the gun, I murdered with a gun, so I will die by the gun," he told loved ones.

The anonymous sharpshooters who killed Gardner came from a volunteer pool of trained law-enforcement officers; those from the area where the crime happened are preferred. Authorities say prison officials typically get more volunteers than they need,, and Gardner's execution was no exception.

Before he was strapped to the steel chair, the five officers on the squad loaded one round into their state-issued rifles. One random cartridge is blank, so no officer is entirely sure if he or she fired a fatal round.

Though Utah had banned firing squads in 2004, lawmakers voted to bring back the procedure in 2015, their response to the shortage of death-penalty drugs. But Goldfarb says if authorities want to be absolutely certain that an inmate dies instantly without pain or suffering, they can choose another target on the body.

"Firing a gun at point blank range into the head" is 100 percent effective, and "would cause a near-instantaneous death. But it would be exceedingly violent and destructive," Goldfarb writes. "But could we ask someone to inflict that kind of violence on another as part of their job as a state employee? If the state were to authorize such a gruesome spectacle in the name of law, how could we maintain our standing in the world as a protector of human rights?"

Still, she predicts the firing squad debate could go far in the current law-and-order climate ushered in with President Donald Trump's inauguration.

"I see the present moment as one in which fair debate based on factual evidence is being threatened and 'fear of the other' who would use violence to harm 'us' is being fanned for political gain," she writes. "These are the emotional conditions that have allowed the death penalty to persist in America – providing a simple answer to a complex problem."

Still, "there may be pockets of renewed death penalty support, using whatever methods are permitted," writes Goldfarb. "But I don't think that approach will become widespread again, as it degrades us as a society and depends on rhetoric that is divisive, cynical, extremely racialized, and ultimately corrosive to America."

In Utah, some lawmakers apparently agree: A bill to completely abolish capital punishment in the Beehive State nearly reached the governor's desk last year. During the legislative debate, Ricky Gardner, Randy Gardner's brother, temporarily disrupted the session, waving enlarged photos of his brother's autopsy, showing a black, grapefruit-sized hole where his heart used to be.

"This is my brother!" Randy Gardner yelled. "Look at that! That's somebody's little brother, that's somebody's dad! That's what the death penalty's done to Utah!"

Around that time, the Salt Lake Tribune went all-in for repealing the death penalty, recalling the state's early history of rough frontier justice, as well as the years (and millions of state taxpayer dollars) it takes for an inmate to exhaust his legal appeals.

Firing squads, the paper declared, are "a relic of a brutal age that casts the state in the most negative light before the world," the paper declared. "The legal, ethical and financial arguments necessary to make the death penalty seem like anything other that what it is – thuggish, expensive vengeance that harms everyone it touches – are getting harder and harder to make, or believe."