A shortage of lethal injection drugs has prompted lawmakers in several death-penalty states to make noise about bringing back more primitive methods of execution.
This week, Tennessee became the first one to actually do it.
Gov. Bill Haslam, a Republican, signed a law late Thursday that would make the electric chair the backup if the state can't obtain the chemicals for its injection protocol.
Prison officials say they are confident it won't come to that, but the prospect sent shudders through some death-penalty experts.
"There have been a lot of horrific electrocutions," said Fordham Law School Professor Deborah Denno, who has studied the electric chair extensively.
"Going back in time is not a good thing."
Here's a look at the past and possible future of the electric chair:
Why is Tennessee using the electric chair as a backup?
Like many states, Tennessee has had difficulty obtaining the chemicals it needs for lethal injections; it has not been able to carry out an execution since 2009 because of drug shortages.
Although the Department of Correction says it is confident it will be able to secure the deadly doses for the 10 men with execution dates, politicians are apparently not as sure.
They drafted a bill that would make the electric chair the automatic backup method, and the governor signed it Thursday night. Previously, electrocution was used only if an inmate convicted before 1999 chose it.
Will the new law stand up to legal challenges?
That remains to be seen. The modern U.S. Supreme Court has not weighed in on whether electrocution amounts to cruel and unusual punishment in violation of the Eighth Amendment of the Constitution.
The high court had agreed to take up the matter after Florida's 1999 electrocution of Allen Lee Davis, who screamed and bled before he died, but it never ruled because the state switched to lethal injection.
Courts in two states — Georgia and Nebraska — have declared the electric chair unconstitutional.
Does Tennessee actually have an electric chair?
The state's original chair — dubbed Old Sparky — was reportedly crafted from the gallows where inmates used to be hanged.
Department of Correction spokeswoman Neysa Taylor refused to answer any questions about the current chair, but a 2007 state report detailed its history.
In 1989, it was rebuilt and outfitted with a new electricity-delivery system by Fred Leuchter, a self-styled execution specialist who was labeled a Holocaust denier by the Anti-Defamation League.
Later, electrical engineer Jay Weichert put in modifications and helped the Correction Department decide on the settings: 1,750 volts at 7 amps cycled on for 20 seconds, off for 20 seconds and on for 15 seconds.
The current chair was first used in 2007 for the execution of Daryl Holton, who shot his four children. Days before, Leuchter claimed it would not work properly and would torture the inmate, but the medical examiner said Holton's death was quick and unremarkable.
Taylor said Friday that the chair is "fully operational."
What can go wrong during an electrocution?
In a 2002 academic paper, Denno documented 19 electrocutions in the previous quarter-century that she described as botched.
"Severe burning, boiling body fluids, asphyxiation, and cardiac arrest, can cause extreme pain when unconsciousness is not instantaneous," she wrote.
Some electrocutions have gone spectacularly awry. In 1997, a mask covering killer Pedro Medina's face burst into flames and shot fire into the air, filling the execution chamber with smoke, witnesses reported.
Proponents say that hundreds of electrocutions have been performed throughout the decades without problems.
How often have electric chairs been used in the U.S.?
According to the Death Penalty Information Center, since capital punishment was reinstated by the U.S. Supreme Court in 1976, 158 prisoners have been electrocuted.
The most recent was Robert Gleason, a three-time murderer who chose to go to the chair in Virginia on Jan. 16, 2013, after killing two fellow inmates to speed up his journey to death row.
The last prisoner who went to the electric chair without being given a choice was Lynda Block, a cop-killer who was executed on May 10, 2002, in Alabama.
Who invented the electric chair?
A Buffalo, N.Y., dentist is said to have come up with the idea of electrocution as an alternative to hanging in 1881.
A few years later, an engineer for Thomas Edison was enlisted to design and build the contraption. He cleverly used alternating current, which was being promoted by industry rival George Westinghouse, in a bid to show that it was more dangerous than Edison's direct current.
On Aug. 6, 1890, it was used for the first time on ax murderer William Kemmler. The execution was a gruesome affair, according to witnesses, who reported that the room filled with the smell of burning flesh and that the initial shock failed to kill the prisoner.
How do Americans feel about the electric chair?
A recent poll by NBC News found that nearly 1 in 5 people are open to the idea of electrocution as the primary form of capital punishment.
Asked which method should be used if lethal injection is no longer viable, 20 percent were for the gas chamber, 18 percent for the electric chair, 12 percent for firing squad and 8 percent for hanging. The remainder said executions should be abandoned if lethal injection was no longer an option.
