The authors of a new study are suggesting that executions carried out by lethal injections possibly cause death by asphyxiation, and the prisoners being executed may be conscious and may experience pain.
The medical review of dozens of executions has concluded that the drugs used to execute prisoners in the United States sometimes fail to work causing slow and painful deaths that probably violate constitutional bans on cruel and unusual punishment.
Researcher Leonidas Koniaris from the University of Miami and colleagues examined data from North Carolina and California along with some information from Florida and Virginia on deaths by lethal injection.
They analyzed details released on 40 prisoners in North Carolina since 1984 and another dozen in California, such as the dose the inmates received, their weight and the time they needed to die; they found the average death time was 10 to 14 minutes.
They concluded that the typical "one-size-fits-all" doses of anesthetic do not consider an inmate's weight and other key factors; some received too little, and in some cases, the anesthetic wore off before the execution was completed.
It is reported that at least one California inmate required a second dose, and additional doses were used in two other executions there.
Amnesty International says in 2005 world wide, 22 countries killed at least 2,148 people by lethal injection; of the 53 executions carried out in the United States in 2006, 52 were by lethal injection.
Lethal injections are currently used for execution in the U.S. and China and have been adopted by 37 states as a cheaper and more humane alternative to electrocution, gas chambers and other execution methods.
But the method has been suspended in 11 states after opponents alleged it is ineffective and cruel.
The issue reached a critical stage last year in California, when a federal judge ordered that doctors assist in killing Michael Morales, convicted of raping and murdering a teenage girl; the doctors refused, and legal arguments in the case have gone on since.
Medical ethics ban doctors and other health professionals from taking part in executions.
The authors say the current cocktail constituting a lethal injection is based on one drawn up by legislators in Oklahoma, and appears to have been based on personal opinion rather than independent research.
They say there is no scientific evidence which has been validated that lethal injection is humane.