Christa Pike was held on a gurney at Riverbend Maximum Security Institution in Nashville for about an hour on Wednesday while, in carrying out her execution, staff repeatedly tried to find a vein, using at least seven needles, her lawyers say. She was then given two doses of pentobarbital, each intended to be fatal, and survived.

Pike, who has never denied her part in the 1995 killing that put her on death row, would have been the first woman executed in Tennessee in more than 200 years. Her lawyers said on Thursday that she was receiving life-saving care in hospital, and that she probably suffered brain damage as a result of the injections.

The execution followed a day of legal wrangling. A federal appeals court briefly halted it, ruling by two votes to one that a stay was needed to examine whether her claims of childhood sexual abuse had been fully considered at sentencing. The US Supreme Court later lifted the stay by six votes to three, allowing the state to proceed before the death warrant expired at midnight.

William Puckett, a presenter and journalist with the local broadcaster WVLT, was among the media witnesses in the observation room. He said Pike was conscious and convulsing on the gurney after the injection began at 7.27pm, a dose that should have killed her within minutes. She then suddenly broke into “a joyful laugh and a giggle”, he told the Daily Mail.

Minutes earlier, Puckett recalled, Pike had begun singing in a high voice, repeating the words of a traditional Buddhist meditation: “Be kind and gentle with yourself and be peaceful.”

As witnesses watched her convulse, Tennessee Department of Correction staff placed a stone in view of the observation room at about 7.41pm to signal that the drug had been fully administered. At 7.44pm Pike spoke to her spiritual adviser, according to the New York Post, and at 7.46pm a curtain was drawn across the window, which usually means an execution is complete.

Witnesses then heard loud snoring from the chamber. Puckett said it sounded like an elderly man asleep, “as if she were enjoying the best sleep of her life”.

The curtain was raised again after three minutes and a second dose was administered. Four minutes later, Pike’s body suddenly convulsed and she took a sharp breath, Puckett said. The curtain came down for a second time at 8.05pm, but the snoring continued for a further 50 minutes.

Behind the curtain, witnesses could hear doctors and lawyers going in and out of the room. Journalists were escorted out at about 8.53pm, with Pike still snoring. She was rushed to hospital soon afterwards.

Helping staff find a vein

According to Pike’s lawyers, quoted by the New York Post, at least seven needles were used, one of which bent as it was removed from her arm. As the procedure descended into chaos, Pike not only cooperated but tried to guide the execution team, pointing to places on her body where she thought a vein could be found.

“Please try higher up, on my shoulder. Try here, I think it will be fine,” she repeatedly told them, according to her lawyer Stephen Ferrell, an assistant federal defender with Federal Defender Services of Eastern Tennessee.

While the intravenous lines were being placed, she reportedly complained of severe pain. “I feel as if my arm is about to explode. One spot is throbbing very badly,” she said, according to Tori Gessner, a reporter with the local broadcaster WKRN, who also witnessed the procedure.

Her defence team says she was restrained for about an hour as staff tried to gain venous access. They say she received two doses of pentobarbital, each meant to be lethal, but that the execution did not go as planned. They blame difficulty accessing her veins and flaws in the execution protocol, which they say they had warned about before the execution.

Her worst fear realised

Her lawyers place particular weight on the fact that Pike had said before the execution that she feared staff would struggle to find her veins. Ferrell said the prolonged procedure was even more traumatic for her because of the sexual abuse she suffered when young, according to the defence.

One of her greatest fears, he said, was being immobilised while her body was repeatedly pierced and interfered with over a long period.

Tennessee Governor Bill Lee, a Republican, has since ordered a comprehensive, independent review of the state’s execution procedures and cancelled the only other execution scheduled in Tennessee this year. It was the second failed execution in the state in five months, according to the Death Penalty Information Center, following that of Tony Carruthers earlier this year.

Pike’s lawyers are now asking for her death sentence to be commuted. They argue that “after 20 years of isolation and an attempt to kill her by lethal injection, Christa has suffered greater punishment than any other human being in the history of the death penalty in the United States”.

The case has prompted fierce debate in Tennessee over execution methods. Republican Senator Marsha Blackburn has called for the electric chair to be reinstated, arguing that the causes of the failure should be investigated.

The murder that put her on death row

Pike was sentenced to death for the murder of Colleen Slemmer, 19, in January 1995. Prosecutors said Pike, then 18, her 17-year-old boyfriend Tadaryl Shipp and another 18-year-old, Shadolla Peterson, lured Slemmer to an isolated spot on the University of Tennessee’s agricultural campus in Knoxville. All four were students on a Job Corps training programme in the city.

Slemmer was tortured and beaten before she died, with authorities saying the attack lasted at least 30 minutes. Pike was sentenced to death in 1996. Shipp, who was a minor at the time of the crime, received a life sentence and remains eligible for parole. Peterson, who testified against the other two, was convicted of being an accessory after the fact.