Although 37 American states use lethal injections to execute prisoners, they also expect the process to be relatively painless. But a controversial new study contends that the three-drug cocktail which is currently used can cause a slow and painful death. Some prisoners apparently suffocate while they are conscious and unable to move. They may even feel as if they were on fire. The study, in the online journal PLoS Medicine, was based on the logs of the executions of 40 prisoners in North Carolina since 1984 and about a dozen in California, supplemented by incomplete information from Florida and Virginia. The journal’s editors have called for the abolition of the death penalty: “There is no humane way of forcibly killing someone.”

The problem seems to be that “one-size-fits-all” injections of anaesthetic do not take into account the prisoner’s weight. Some received too little and in some cases the anaesthetic wore off before the execution was complete. But since none of the patients are available for questioning about what they felt, it is difficult to gather incontrovertible evidence. The methodology of a 2005 study by the same authors was criticised. In any case, supporters of the death penalty may not care too much. A prosecuting attorney in Indiana, where an execution is to take place on Friday, told the Washington Post: “It doesn’t matter a whole lot to me that someone may have felt some pain before they were administered poison as a method of execution.”