The female inmate who survived a failed execution in a US prison last week is now conscious and speaking, but her prognosis remains unclear, her lawyers said Tuesday.

Christa Pike, 50, who was sentenced to death for a murder she committed when she was a teenager, received two supposedly lethal doses of the drug pentobarbital at a Tennessee prison a week ago.

She survived the injections, however, and was rushed to hospital, where she had been unconscious and on a ventilator in critical condition.

Pike's lawyers said that "against all odds" she was now "conscious, speaking, and continues to receive critical medical care."

"Despite the severe damage she endured to her arms, she is still handcuffed and shackled to the bed," they said. "Her recovery is medically unprecedented. Her prognosis remains unclear but, at a minimum, we expect a long recovery."

Her lawyers repeated a call for Tennessee Governor Bill Lee to commute Pike's sentence to life imprisonment without the possibility of parole.

Lee suspended the carrying out of capital punishment in the southern state following the failed execution pending an independent investigation. The prison chief has resigned.

Pike's case sparked debate over the death penalty for young offenders, as she was 18 when she and her boyfriend beat and killed 19-year-old Colleen Slemmer at a job training camp in 1995.

The killing gained national attention after Slemmer's body was found with a pentagram, often seen as a satanic symbol, carved in her chest.

Pike's lawyers sought clemency citing her age, childhood sexual abuse and mental health problems, including post-traumatic stress disorder.

According to the Death Penalty Information Center, which publishes data and analysis on capital punishment in the United States, Pike is the first inmate ever to survive "after being injected with lethal doses of execution drugs."

© Agence France-Presse