Condemned US murderer Christa Pike remains critically ill in a Nashville hospital with an unclear prognosis after surviving two attempts to execute her by lethal injection.

The 50-year-old was taken to hospital following the failed execution attempts on Wednesday, where medical teams are still trying to clear two doses of pentobarbital from her body, according to her lawyer Stephen Ferrell.

Mr Ferrell said on Sunday that he does not believe Pike has regained consciousness at any stage since the procedure was halted. He explained that he has been receiving condition updates through her medical power of attorney rather than speaking directly with her doctors.

The fallout from the incident was swift across Tennessee's penal system. State Governor Bill Lee has suspended all executions for the remainder of the year, while the state's prison chief announced on Saturday that he will be resigning from his post.

Pike was sentenced to death in 1996 following the murder of 19-year-old Colleen Slemmer in Knoxville the previous year. Pike was 18 at the time when she and her then-boyfriend, Tadaryl Shipp, beat, tortured and killed Slemmer.

Ms Slemmer's mother, May Martinez, had travelled to Nashville to witness the execution after years of backing the death sentence. She said she broke down in tears upon hearing that the lethal injection had not been successful.

Prior to the scheduled execution, Pike's legal team had lodged warnings regarding her specific medical background and anatomy. They pointed out that conditions including thrombocytosis — a blood-clotting disorder — alongside unusually small veins created a significant risk of unnecessary pain and suffering during lethal injection.

For its part, the Tennessee Department of Correction has defended its lethal injection procedures. The agency stated that the established protocol does not allow for additional measures beyond what staff carried out on Wednesday.

What remains unresolved is what happens to Pike legally if she survives. Mr Ferrell noted that significant questions will surround her mental and physical state, saying: "If she recovers - she may not fully recover - and there may be issues about her competence. I mean, we just don't know any of this."

He added that the defence team has had no discussions regarding future legal moves, noting: "The Tennessee attorney general's office so far has not given us any indications of what their intentions will be."

State authorities have not yet explained what caused the execution to fail, nor have they confirmed whether they intend to seek another execution date once the current moratorium ends.

I'll be following this one closely as state officials review the protocol — check back for updates as soon as we learn more.