How did US death row inmate Christa Pike survive two execution attempts via lethal injection? What experts say...

Christa Pike, the Tennessee death row inmate who survived two execution attempts via lethal injection, is now fully conscious and speaking as she receives treatment at a hospital, her attorneys say.

The 50-year-old survived two doses of pentobarbital, a sedative, as officials attempted to put her to death last Wednesday. She was set to be the first woman executed in Tennessee in 200 years. She is also believed to be the only person to survive after receiving a lethal injection drug.

In a statement, Pike’s attorneys said, “Against all odds, Christa Pike is 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. Her recovery is medically unprecedented. Her prognosis remains unclear but, at a minimum, we expect a long recovery.”

“She is the only person known to have survived a complete execution attempt in the US. Christa is a survivor and will take recovery one day at a time. We continue to ask the Governor of Tennessee to commute Christa Pike’s sentence to life imprisonment without the possibility of parole,” Pike’s attorneys added.

Deborah Denno, a criminologist and professor at Fordham Law School, told the BBC that she was "absolutely astonished" that Pike was conscious and speaking.

Pike "is the only person for whom some kind of toxin has been injected", she said.

"They did everything they were supposed to do as part of the execution process, and it simply didn't work," Denno said. "This has never happened before."

Experts are focused on whether an issue with the IV line caused the drug to pool in her tissue instead of entering her bloodstream.

A court filing said Pike’s arms were swollen, burned and blistered when she arrived at the hospital.

Dr Joel Zivot, an anaesthesiologist advising Pike's defence team, told the BBC that the likelihood of surviving the lethal injection was low and said that it was unusual that she survived it. "I would not, in any way, say at this point that all the big risks are behind her," he noted.

Zivot said that one possible explantion was that, instead of the dose entering Pike's bloodstream, the pentobarbital could have spread across the tissue under her skin.

Witnesses to the attempted execution said they saw Pike choking and struggling for an hour after she received the first injection. She was hospitalised after a second dose failed to kill her.

One of Pike’s lawyers called the process “cruel and torturous”. He said he counted seven needles in Pike’s left arm, one of which was bent.

Her lawyer had warned that officials may struggle to locate her vein and cause her suffering during the process, but he stated he had pushed to proceed, the Guardian reported,

Her lawyers are due in court on Wednesday seeking an order requiring the prison system to preserve evidence including drug lot numbers, needles and execution logs.

Pike was sentenced to death for the killing of 19-year-old Colleen Slemmer in 1995, when she was 18, along with her boyfriend. Pike had cut Slemmer’s stomach and throat with a box cutter before smashing her head with a rock. Her boyfriend, Tadryl Shipp, then carved a pentagram into the victim’s chest. They also showed a part of the victim’s skull to a classmate.

Shipp was convicted of first-degree murder and given a life sentence.

Pike never denied her role in the murder. She was later diagnosed with bipolar disorder and PTSD. While on death row, she underwent nearly 30 years of solitary confinement.

Governor Bill Lee called the incident deeply disturbing and ordered a comprehensive probe. He also suspended executions in the state pending the investigation. The prison chief has resigned.

Pike's lawyers meanwhile called on Lee to commute her sentence to life imprisonment without parole. Tennessee's Catholic Bishops and the Episcopal bishops issued a joint statement on October 1, asking the governor to spare Pike’s life and prevent another attempt to carry out the death sentence. They called the death penalty "an attack on human dignity and unnecessary to protect society while still punishing those convicted of horrible crimes.”