A WA coroner has found inadequacies in the mental health system were not to blame for the suicide of a 39-year-old Perth woman.

The severely depressed woman, known only as Ms D, travelled to Mexico and overdosed on a euthanasia drug in May 2008.

She had been committed to the King Edward Memorial Hospital against her will three months earlier but discharged herself after her involuntary patient status was downgraded to voluntary.

Her family believes mental health authorities failed to protect her by discharging her despite staff finding evidence of her suicide plan.

The family is suing the Health Department for negligence.

Coroner Evelyn Vicker found while the woman’s supervision, treatment and care was not optimal, there was nothing to suggest it was below accepted practice at that time.

She said it was a tragic outcome, but did not accept that the woman should have been under constant supervision, saying that could have made her mental condition worse.

Ms Vicker found the doctor treating Ms D was not of the view she “possessed a level of depression that would lead to suicide on its own” and that Ms D appeared to “comply with treatment and supervision” but she was able to adopt certain behaviours to speed up the process than if she continued to reject help.

“It is not clear the deceased ever properly accepted she was in need of help,” she said.

“The deceased used the hearing at the Mental Health Review Board to convince the members she was quite rational and able to make appropriate choices for her wellbeing.

“She effectively convinced the board, she would be better off without restrictions imposed by her involuntary status.”