A Tennessee death-row inmate remained alive after authorities administered what her lawyers say were two doses of the lethal injection drug during her scheduled execution.
Christa Pike was due to be executed at Riverbend Maximum Security Institution in Nashville on Wednesday morning, but the execution was delayed following a last-minute legal challenge.
The US Supreme Court later allowed the execution to proceed.
Pike’s lawyers subsequently filed an emergency petition seeking to halt the execution, alleging that their client had received two syringes of pentobarbital but had not lost consciousness and still had a heartbeat.
Witnesses who observed the execution described the process as unusually prolonged. Associated Press journalist Kim Chandler said Pike appeared to be awake when the procedure began and was later heard gasping and snoring.
The curtain to the execution chamber was reportedly closed several times before media witnesses were eventually ordered to leave the prison.
Emergency service teams were also seen outside the facility.
Prison officials had not confirmed Pike’s condition or announced a time of death at the time of the reports.
Pike, 50, was sentenced to death for the 1995 murder of 19-year-old Colleen Slemmer, whom she met at a training programme. Pike was 18 when the killing occurred.
Her lawyers had argued for the execution to be halted, while Pike had previously said she was not afraid to die.
