Christa Pike, the only woman on death row in Tennessee, is set to become the first female executed in the state in around 200 years when she faces lethal injection on September 30. Her legal team is now fighting to have that sentence commuted, arguing that the state is incapable of carrying out the execution without causing serious pain and suffering.

Pike was 18 when she lured classmate Colleen Slemmer into woodland in Knoxville, Tennessee in 1995, believing Slemmer was trying to steal her boyfriend. Along with two accomplices, she beat, stabbed and bludgeoned Slemmer before carving a pentagram into her forehead and chest. Prosecutors said Pike kept a piece of her victim's skull as a trophy and later bragged about the murder to fellow students, dancing and singing as she described what she had done. She was convicted of first-degree murder in 1996 and became the youngest person on death row at 20. In 2003 a further 25 years was added to her sentence after she attempted to strangle a fellow inmate with a shoelace.

Her lawyers have cited a failed execution attempt in May this year as evidence that the state lacks the qualified medical personnel to carry out lethal injections without incident. During that procedure, medical staff were unable to find a suitable second vein in the condemned man, and the execution was called off. A witness described watching him "wincing and groaning" throughout.

Pike's legal team argues her case carries even greater risk. She has a blood-clotting condition called thrombocytopenia, bipolar disorder, PTSD, and what her lawyers describe as "small veins that make insertion of a needle difficult, even for the most trained medical professionals." They warn this combination makes a prolonged and painful execution a real possibility.

Her attorneys have called on Tennessee to commute her sentence, citing her youth at the time of the crime, her severe mental illness, and the physical and sexual abuse she suffered throughout her childhood. "With time and treatment," they wrote, "Christa has become a thoughtful woman with deep remorse for her crime."

They are also asking the Tennessee Supreme Court to appoint a special master to investigate their concerns independently ahead of the September 30 date.