The drug used for lethal injection is made by European drug makers who have recently stopped selling the deadly chemical to American jails on ethical grounds. Capital punishment is outlawed across Europe and lawmakers have made it harder for companies to supply the United States, one of only two democracies still allowing capital punishment, the other being Japan.

A member of the European Parliament said: "By persuading responsible pharmaceutical companies to supervise their distribution chain and by getting controls on exports from Europe tightened, U.S. prisons' ability to procure their death machine supplies has been thwarted."

When states cannot buy pentobarbital for injections on the market, they resort to getting it from other places or using a two- or three-drug cocktail instead. "At least two recent executions are also raising concerns about the drugs' effectiveness. Last week, Ohio inmate Dennis McGuire took 26 minutes to die by injection, gasping repeatedly as he lay on a gurney with his mouth opening and closing. And on January 9, Oklahoma inmate Michael Lee Wilson's final words were, 'I feel my whole body burning,'" says a source questioning the validity of the drug.

Unlike the Europeans imagined, this has not resulted in a change to capital punishment laws but instead has spurred lawmakers to bring back execution methods from the past, such as firing squads, gas chambers and the electric chair.

Wyoming Republican state Senator Bruce Burns has said that death by firing squad would be far less expensive than building a gas chamber. Virginia Republican Jackson Miller is sponsoring a bill that would allow for electrocution if lethal injection drugs are not available.

While lethal injection is considered the most clinical method of execution due to the sedatives present, some states offer alternatives to the convicted. Alabama, Arkansas, Florida, Kentucky, Oklahoma, South Carolina, Tennessee and Virginia still have electric chair as an option.

Arizona, Missouri and Wyoming allow for gas-chamber executions and Delaware, New Hampshire and Washington allow inmates to choose hanging. Two prisoners chose hanging in 1993 and 1994. Firing squads take place exclusively in Utah, where there have been three civilian firing squad executions.