Tennessee death row inmate Christa Pike is in "critical condition, receiving life-saving care" at hospital, after surviving two lethal injection attempts, leading the state's governor to halt all executions for the year." We don't have a sense of her prognosis or much update on her health at the moment," her lawyer Randy Spivey told reporters on Thursday.

" But we do know that she is alive right now." Her lawyers are now asking for her sentence to be commuted.

Pike, 50, was sentenced to death in 1996 for the murder of Colleen Slemmer. She was injected with two lethal doses of pentobarbital on Wednesday but remained alive, her lawyers said.

She was then sent to hospital in an ambulance. Pike was 18 when she and her then-boyfriend, Tadaryl Shipp, beat, tortured and killed 19-year-old Slemmer.

Her attempted execution on Wednesday was the subject of a last-minute legal battle. This culminated in the US Supreme Court allowing the lethal injections to go ahead.

On Thursday afternoon, Pike's lawyers offered more details about what happened during the attempted execution, describing a harrowing scene shrouded in secrecy. " Last night, the execution team attempted to establish an IV line for an hour," Spivey said.

" I counted at least seven needles used in her left arm alone, one of which appeared to be bent when it was pulled from her arm after an unsuccessful attempt." Spivey said that observers were kept in a dark room behind a closed curtain, after the second lethal dose had been administered and "it was clear that Miss Pike was still breathing" minutes later."

No-one knew what was going on behind that curtain," Spivey said. " I had no idea when and if medical professionals began to assist."

Spivey said the state's governor must commute Christa's sentence now, a request that was denied previously. Stephen Ferrell, another of Pike's lawyers, said they were also looking at other legal options.

" We want to think this through and we want to make sure that Christa recovers and has some input in what she wants," he said. Tennessee Governor Bill Lee has ordered an independent review and said on Thursday the investigation into Pike's botched execution "will be thorough", adding that "it's going to take time"."

There are a lot of questions," Lee said. " The people of our state deserve to have those questions answered, and that's what this investigation is for."