Some prisoners executed by lethal injection in the US may die of suffocation while still conscious and in pain, researchers said.
Drugs used to execute prisoners in the U.S. sometimes fail to work, causing slow and painful deaths that probably violate constitutional bans on cruel and unusual punishment, a new medical review of dozens of executions concludes.
Even when administered properly, the three-drug lethal injection method appears to have caused some prisoners to suffocate while they were conscious and unable to move, instead of having their hearts stopped while they were sedated, scientists said in a report.
Lethal injection is the primary method of execution for 37 US states and the federal government, but 11 states have halted or suspended the procedure because of legal or ethical questions.
The drugs used are the anaesthetic thiopental, pancuronium bromide to paralyse the muscles and lungs, and the electrolyte potassium chloride to stop the heart.
Since the US Supreme Court upheld the death penalty in 1976, the United States has executed 1070 people, 901 of them by lethal injection, according to the Death Penalty Information Centre.
The study, published in the Public Library of Science journal PLoS Medicine.
