Nashville, Tennessee - Convicted killer Christa Pike, who survived a botched execution last week, was almost taken off life support before she regained consciousness, her lawyer said Wednesday, as a court ordered prison authorities to preserve evidence in the case.

"On Monday night, it was our understanding that Christa was brain dead, and that life support would be removed the next day," Pike's lawyer Randy Spivey told reporters.

"But on Tuesday, to the shock of everyone... Christa woke up and began talking."

The 50-year-old woman, 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 last Wednesday.

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

Pike remains shackled to her hospital bed, awake and able to speak a little but incapable of swallowing or moving her arms, according to her attorneys.

"She cannot move either of her arms, both of her arms and hands are tremendously swollen, and we do not know what, if any, function she will regain in her arms," Spivey said, adding that "there's a long road ahead" for her recovery.

"Medical staff have asked that the shackles be removed and have been denied that request," Pike's lawyer Luke Ihnen said at a court hearing.

An anesthesiologist retained by Pike's lawyers as an expert ahead of her execution told the BBC that she was off the ventilator.

She has "no memory, I believe, of the execution attempt," Joel Zivot said, adding that Pike knows her name and thinks it is currently September.

"We have to ask how much suffering is enough? We continue to ask [Tennessee Governor Bill Lee] to commute Christa's death sentence" to life in prison, Spivey said.

The court ordered state corrections officials to preserve all evidence related to the botched execution, including medical supplies, waste, and audio and video recordings.

Pike's fate revived debate over capital punishment in the US.

Lee suspended executions in Tennessee pending an independent investigation, and the state's prison chief resigned. Tennessee's correction department has maintained that it followed established protocol.

Texas was scheduled to carry out an execution later Wednesday, the first in the US since the attempt to put Pike to death.

Jamaal Howard was set to die by lethal injection for killing a store clerk during a 2000 robbery.

His lawyers have sought to have his execution postponed, citing Pike's case.

The Death Penalty Information Center, which publishes data and analysis on capital punishment in the US, said Pike was the first inmate to survive after being injected with lethal doses of execution drugs.

Pike was 18 when she and her boyfriend beat and killed 19-year-old Colleen Slemmer at a job training camp.

Pike would have been the first woman put to death by the state of Tennessee in more than 200 years, according to the Death Penalty Information Center.

Excluding Pike's failed execution, there have been 29 executions in the US this year, which have all been carried out by lethal injection.

The death penalty has been abolished in 23 states, while three others – California, Oregon, and Pennsylvania – have moratoriums in place.

The Pentagon said on Monday that President Donald Trump has approved the execution of Nidal Hasan, a US Army psychiatrist who shot dead 13 people and wounded more than two dozen at Fort Hood in Texas in 2009.

Hasan's execution by firing squad, set for December 3, would be the first carried out by the US military since 1961.