Christa Pike is now awake and speaking in hospital after surviving two lethal injections during a failed execution attempt.

Christa Pike is now awake and speaking in hospital after surviving two lethal injections during a failed execution attempt. 

The 50-year-old was set to become the first woman executed in Tennessee in over 200 years before the process went wrong last week.

Witnesses described hearing her gasping, moaning, and snoring behind a closed curtain after receiving two separate doses of pentobarbital.

An ambulance carried her away from the Nashville prison to an intensive care unit, where she remained on a ventilator until today.

Her attorneys say her recovery is "medically unprecedented" after surviving the two lethal doses.

"Despite the severe damage she endured to her arms, she is still handcuffed and shackled to the bed," her legal team said in a statement.

Medical experts warning her prognosis remains unclear say it could take months to evaluate her long-term condition.

Dr Joel Zivot, an anaesthesiology professor who consulted for the legal team, warned that she is not yet free of serious risk.

"She has recovered to a certain degree that she's able to be off a ventilator and able to speak, but in no way would I announce her free of further serious risk," Dr Zivot said.

Pike was sentenced to death in 1996 for the 1995 murder of 19-year-old Colleen Slemmer.

Under US constitutional law, prisoners cannot be executed if they lack the mental capacity to understand their punishment.

Tennessee officials have not yet confirmed whether they will attempt a second execution.