Christa Pike, a murder convict in the US, was reportedly taken to a hospital on Thursday after she survived a second dose of lethal injection.
According to news agency AP, Pike's legal team filed a motion to halt the execution, stating she still had a heartbeat and was snoring during the procedure in Tennessee.
Robin M. Maher, executive director of the Death Penalty Information Center in the US, said Pike's experience was 'singular and unparalleled', reported AP.
She is being treated at a hospital, though her condition remains unclear. Pike would have been the first woman to be executed in the state in more than 200 years.
Pike, 50, had been sentenced to death in 1996 for torturing and killing 19-year-old Colleen Slemmer. She was 18 then and had committed the crime with the help of her then-boyfriend, Tadaryl Shipp.
Pike's legal team said she had been given two doses of pentobarbital, a potent sedative that slows down the body, including the nervous system. It can be lethal in high doses.
The Tennessee Department of Correction has justified the execution method. It said the execution attempt followed every 'lawful step as per the established protocol approved by the Attorney General's Office'.
However, media witness reports detailed what happened in the execution chamber. Pike was awake at one point and asked the prison officials if her arm was supposed to feel that way, a media witness said. In the US, media witnesses are journalists permitted to observe executions and report what happened to the public.
A media witness who was present at the execution attempt said that Pike was heard snoring even after the second dose had been administered.
In May this year, the state of Tennessee could not execute Tony Carruthers, a man convicted of kidnapping and killing three people in 1994. In his case, the executioners could not find a vein to administer pentobarbital despite trying for over an hour.
Twenty-seven of the 50 states in the US have the death penalty, while it is abolished in the other 23.