NewScientist.com news service
The three-drug cocktail used to execute prisoners in the US by pain-free lethal injection is inherently flawed and will not reliably anaesthetise inmates as they are put to death, a new study suggests.
The three drugs that make up the lethal-injection cocktail, which is used in most US states, are each thought to be lethal in their own right. However, Teresa Zimmers at the University of Miami in Florida, US, and colleagues found that the drug combination protocols used by executioners may not be reliable.
"Even if all the drugs are delivered intravenously in the quantities specified, they still may not produce death reliably," says Zimmers.
The researchers found that the average concentrations of the anaesthetic sodium thiopental varied enormously per kilogram of body weight, from 10 milligrams to 75 mg. In surgery, concentrations greater than 10 mg/kg are used for general anaesthesia.
Worse, execution logs showed that inmates' hearts continued beating 2 to 9 minutes after potassium chloride – the second drug in the cocktail – was administered.
"Potassium chloride usually causes instantaneous cardiac arrest once it reaches the heart," says Jonathan Groner at Ohio State University in the US. Groner suggests its effectiveness may be reduced somehow due to the combination of drugs used in the injection.
Lastly, pancuronium bromide is used to paralyse the muscles and stop breathing. Of the three drugs, it is the only one that Zimmers' team says is able to induce death reliably in the doses they examined. This means that even if executioners properly administer the entire course of drugs, there remains the possibility that the condemned may die of asphyxiation and be aware of it as it happens.
Despite the new findings' potential impact on US policy regarding execution, Zimmers says she is opposed to offering any advice that may improve lethal injection methods.
"I think it's unethical to comment on how to improve lethal injection protocols," she says. "It's a perversion of everything we as physicians try to do."
The new study adds to a growing body of evidence suggesting that inmates may endure suffering during execution. Tales of gruesome deaths have largely led to electric chairs and gas chambers being abandoned in favour of a supposedly painless lethal injection, which is now used in 37 of the 38 states that sanction capital punishment.
In a previous study, in 2005, Zimmers' team investigated the effectiveness of the anaesthesia given to inmates prior to execution. They found that the levels of anaesthetic sodium thiopental in the blood of inmates were low enough that they may have experienced pain (The Lancet, vol 365, p 1412).
The researchers' findings, and evidence of ageing facilities and poorly trained executioners, led federal judge Jeremy Fogel to rule in February 2006 that California's injection programme was unconstitutional because it represented "cruel and unusual punishment".
There was no way to tell reliably whether inmates were unconscious before drugs were given to induce paralysis and cardiac arrest, he ruled, saying: "[California's] implementation of lethal injection is broken, but it can be fixed." Ten other states have also put injections on hold citing similar concerns.
Journal reference: PLoS Medicine (DOI: 101371/journal.pmed.0040156)