Tennessee death row inmate awake and speaking after surviving two lethal injections

Pike, 50, remains in hospital receiving critical medical care after being unconscious for several days while doctors worked to clear the drug from her body. Her lawyers said her prognosis remains unclear and that they expect a lengthy recovery.

Criminologist Deborah Denno of Fordham Law School told the BBC that seven other prisoners are known to have survived attempted executions, but in those cases executioners were unable to inject the lethal drugs.

Pike appears to be the first known person to survive after the drug was actually administered.

“They did everything they were supposed to do as part of the execution process, and it simply didn't work,” Denno said. “This has never happened before.”

Tennessee authorities have not explained why two doses of pentobarbital failed to kill Pike or said whether they will attempt to execute her again.

Gov. Bill Lee has suspended all executions in Tennessee for the rest of the year, while the head of the state's prison system said he plans to resign.

An anesthesiologist advising Pike's defense team said one possible explanation was that the pentobarbital spread into tissue under her skin instead of entering normal blood circulation. He cautioned that significant medical risks remain.

Pike was sentenced to death for the 1995 torture and murder of 19-year-old Colleen Slemmer. Her lawyers are asking Lee to commute her sentence to life in prison without parole.