Republican Gov. Bill Haslam on Thursday signed a bill into law allowing the state to electrocute death row inmates in the event the state is unable to obtain drugs used for lethal injections. 
 
 Tennessee lawmakers overwhelmingly passed the electric chair legislation in April, with the Senate voting 23-3 and the House 68-13 in favor of the bill. 
 
 Richard Dieter, the executive director of the Death Penalty Information Center, said Tennessee is the first state to enact a law to reintroduce the electric chair without giving prisoners an option. 
 
 "There are states that allow inmates to choose, but it is a very different matter for a state to impose a method like electrocution," he said. "No other state has gone so far." 
 
 Dieter said he expects legal challenges to arise if the state decides to go through with an electrocution, both in terms of whether the state could prove that lethal injection drugs were not obtainable and on the grounds of constitutional protections against cruel and unusual punishment. 
 
 A Haslam spokesman confirmed to The Associated Press that the governor had signed the measure Thursday evening , but offered no further comment. 
 
 States have found themselves running out of drugs used to execute prisoners after a European-led boycott drug sales to prisons. 
 
 Republican state Sen. Ken Yager, a main sponsor of the electric chair measure, said in a recent interview that he introduced the bill because of "a real concern that we could find ourselves in a position that if the chemicals were unavailable to us that we would not be able to carry out the sentence." 
 
 A Vanderbilt University poll released this week found that 56 percent of registered voters in Tennessee support the use of the electric chair, while 37 percent are against it. 
 
 Previous Tennessee law gave inmates who committed crimes before 1999 the choice of whether they wanted to die by electric chair or lethal injection. The last inmate to be electrocuted was Daryl Holton, a Gulf War veteran who killed his three sons and a stepdaughter with a high-powered rifle in Shelbyville garage in 1997. He requested the electric chair in 2007. 
 
 A provision to apply the change to prisoners already sentenced to death has also raised a debate among legal experts. 
 
 Nashville criminal defense attorney David Raybin, who helped draft Tennessee's death penalty law nearly 40 years ago, has said lawmakers may change the method of execution but they cannot make that change retroactive. To do so would be unconstitutional, he said. 
 
 Supporters of the bill requested a legal opinion from state Attorney General Bob Cooper, who said the law would pass constitutional muster, but there was no guarantee it would not be challenged in court. 
 
 Thirty-two states have the death penalty, and all of them rely at least in part on lethal injection. Fewer than a dozen regularly carry out executions, among them Alabama, Arizona, Florida, Georgia, Mississippi, Missouri, Ohio, Oklahoma, Virginia and Texas, which leads the country. The federal government also uses lethal injection but rarely carries out executions. 
 
 The Supreme Court has never declared a method of execution unconstitutional on the grounds that it is cruel and unusual. It upheld the firing squad in 1879, the electric chair in 1890 and lethal injection in 2008. 
 
 The court made it clear over the years that the Eighth Amendment prohibits inflicting pain merely to torture or punish an inmate, drawing a distinction between a method like electrocution and old European practices such as drawing and quartering. The Constitution prohibits "unnecessary and wanton infliction of pain," the court said in 1976. ||||| Story highlights Tennessee death row inmates will be electrocuted if lethal injection drugs are unavailable 
 
 It is the only state to make electrocution mandatory 
 
 In other states that use the electric chair, it is an option 
 
 Drugs for lethal injections have been in short supply 
 
 As controversies over lethal injection drugs surge, Tennessee has found a way around the issue: It is bringing back the electric chair. 
 
 Eight states authorize electrocution as a method of execution but only at the inmate's discretion. 
 
 Now Tennessee is the first state to make use of the electric chair mandatory when lethal injection drugs are unavailable. 
 
 Tennessee Gov. Bill Haslam signed the measure into law Thursday. 
 
 "This is unusual and might be both cruel and unusual punishment," said Richard Dieter, president of the Death Penalty Information Center. 
 
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 "No state says what Tennessee says. This is forcing the inmate to use electrocution," according to Dieter, who believes "the inmate would have an automatic Eighth Amendment challenge." 
 
 The amendment protects against cruel and unusual punishment. 
 
 "The electric chair is clearly a brutal alternative," Dieter said. 
 
 Controversy over lethal injections has been brewing in recent years after European manufacturers, including the Denmark-based manufacturer of pentobarbital, banned U.S. prisons from using their drugs in executions. 
 
 In April, a botched lethal injection in Oklahoma catapulted the issue back into the international spotlight. It was the state's first time using a new, three-drug cocktail for an execution. Execution witnesses said convicted murderer and rapist Clayton Lockett convulsed and writhed on the execution gurney and struggled to speak, before officials blocked the witnesses' view. Lockett died 43 minutes after being administered the first drug, CNN affiliate KFOR-TV in Oklahoma City reported. 
 
 Earlier this year, a convicted murderer and rapist in Ohio, Dennis McGuire, appeared to gasp and convulse for at least 10 minutes before dying from the drug cocktail used in his execution. 
 
 In 2009, the U.S.-based manufacturer of sodium thiopental, a drug also commonly used in executions, stopped making the painkiller. 
 
 Many states have scrambled to find products from overseas or have used American-based compounding pharmacies to create substitutes. 
 
 This month, a group of criminal justice experts recommended that federal and state governments move to a single lethal drug for executions instead of complex cocktails that can be botched. 
 
 The controversy over legal injection drugs raises the question of when a case will arise to test the new law. 
 
 The last death penalty by electrocution in Tennessee was that of Daryl Holton in 2007. 
 
 Holton -- a convicted murderer who killed his three young sons and his ex-wife's daughter -- elected to be killed by the electric chair. 
 
 Before Holton's execution, Tennessee had not used the electric chair in 47 years.
– Amid shortages of drugs used in lethal injections and controversy over a botched execution in Oklahoma, Tennessee has become the first state to revive an older method of execution. Gov. Bill Haslam yesterday signed a bill allowing the state to use the electric chair if execution drugs are not available, the AP reports. State lawmakers overwhelmingly approved the bill last month. Other states allow condemned inmates to choose the chair, but Tennessee is the first to reintroduce it without giving prisoners a choice, according to the Death Penalty Information Center. Wyoming, meanwhile, says it's all out of execution drugs, and lawmakers are drafting a bill to bring back the firing squad—though the ABA Journal points out that the state has but a single inmate on Death Row (that would be 69-year-old Dale Wayne Eaton, who was found guilty of the 2004 murder of an 18-year-old woman). State law currently permits death-by-gas-chamber, but the state doesn't actually have a gas chamber. (A recent poll found that one in five Americans supports bringing back gas chambers.)