The head of prisons in the US state of Tennessee has resigned following the failed execution of death row inmate Christa Pike.
Tennessee Governor Bill Lee announced the resignation of Department of Correction Commissioner Frank Strada on Saturday, saying the commissioner had chosen to step down in the best interests of the state.
Strada said the decision was in the state's best interests and described an ongoing investigation into the incident as "entirely appropriate and necessary".
Pike, who was sentenced to death in 1996 for the murder of 19-year-old Colleen Slemmer, survived two injections of the lethal drug pentobarbital on Wednesday and remains in critical condition at a hospital in Nashville.
Her lawyers have called Strada's resignation "justified" but said "it does nothing to help Christa now".
They said the failed execution reflected "a systemic failure that goes far beyond any one person" and called for an independent review of Tennessee's death penalty system.
Governor Lee has ordered an independent investigation into the attempted execution and halted all executions in Tennessee for the remainder of the year.
Legal filings say doctors are treating Pike at a Nashville hospital and attempting to clear the drugs used during the execution from her body.
Her lawyers said she could be heard crying, whimpering and breathing loudly during the procedure. By Thursday night, she was unconscious, intubated and on a ventilator.
Tennessee's Department of Correction has defended the execution protocol, saying "the protocol does not allow for additional procedures beyond what was carried out".
Authorities have not said whether they will attempt to execute Pike again or explained what went wrong during the procedure.
Her lawyers have filed an emergency motion seeking to preserve "any and all evidence" linked to the failed execution.
Pike's legal team had previously warned that her medical history, including thrombocytosis, a blood-clotting condition, and small veins, increased the risk of pain and suffering during lethal injection.
The execution proceeded after several last-minute legal challenges failed, including two separate appeals rejected by the US Supreme Court.
Governor Lee also denied a clemency request from Pike, who is the only woman on Tennessee's death row.
Pike was 18 when she and her then-boyfriend, Tadaryl Shipp, beat, tortured and killed Slemmer in Knoxville in 1995. She was sentenced to death the following year.