The family of a policewoman who took her own life is suing the state of New South Wales for millions of dollars, for allegedly failing to protect her from harm.

Key points: Andrew McDonald has filed three negligence claims against the state

Andrew McDonald has filed three negligence claims against the state The claim alleges his wife did not receive adequate care after attending several traumatic incidents

The claim alleges his wife did not receive adequate care after attending several traumatic incidents It also alleges police failed to investigate a previous suicide attempt

Newcastle mother-of-two Sergeant Gabrielle McDonald developed post-traumatic stress disorder (PTSD) and depression after witnessing a string of horrific incidents on the job.

She took her own life on July 3, 2013, the day after a police medical officer had declared her as fit for duty.

Her husband Andrew McDonald has filed three negligence claims against the state of NSW on behalf of himself and his two children, Jessica and Joshua.

His statement of claim, filed to the NSW District Court, said over the course of her career, McDonald attended numerous traumatic incidents, including domestic disputes, assaults, car accidents, suicides and murders.

She was particularly distressed by the drowning of a 17-year-old boy in 2009 and a double road fatality in 2010, but did not receive any counselling, debriefing or monitoring after the incidents, the statement of claim alleges.

Got a confidential news tip? Email ABC Investigations at investigations@abc.net.au For more sensitive information: Text message using the Signal phone app +61 436 369 072 No system is 100 per cent secure, but the Signal app uses end-to-end encryption and can protect your identity. Please read the terms and conditions.

In late 2010, she was promoted to Detective Sergeant in the Professional Standards Unit, Northern Region. But she struggled with the heavy workload, which included two stints relieving for her supervisor.

In 2012, McDonald attempted suicide in an office at the Newcastle police station, but police never investigated the incident.

"It's investigation 101," Mr McDonald, who was also a police officer, told the ABC.

"That's what police do and it's appalling that it was never done."

Police medical officer found suicide attempt 'was not genuine'

Andrew McDonald says police failed to investigate his wife's suicide attempt. ( Supplied )

The day before McDonald took her own life, she was sent to see a police medical officer, Dr Naresh Verma.

Mr McDonald told the ABC, Dr Verma determined her previous suicide attempt was not genuine and he did not believe she had PTSD.

"All the staff thought well, OK, things must be on the improve, maybe Gabrielle is not sick at all, maybe she's pulling the wool over our eyes and that was clearly wrong," Mr McDonald said.

Dr Verma did not respond to repeated requests for comment.

McDonald suffered depression after witnessing a string of horrific incidents on the job. ( Supplied )

The police force determined that McDonald should be transferred to another police station the next day.

According to the statement of claim, she was summoned to a meeting without warning and without a support person to be told she was being moved.

McDonald left the meeting in a distressed state, drove to a state forest and took her life.

Mr McDonald said he had one last telephone conversation with his wife.

"She said I can't go on any more. I'm not getting better. I'm such a burden. They keep kicking me down at work. All I'm trying to do is keep my hours up. You know, this is hopeless," he said.

"And I said: 'You can't do this'. I pleaded with her and begged her not to.

"She said I love you and the kids. We talked about all the things we'd done together, but nothing I said would make sense to her, she was just that determined to do it".

McDonald 'did not receive proper monitoring'

Mr McDonald's lawyers allege that the police service ought to have known the meeting would cause her distress and that she was at risk of self harm.

They allege the NSW police force was negligent because it failed to maintain a safe system of work to avoid injury to McDonald.

It had also allegedly failed to provide her with adequate training to perform her duties and to take precautions for her safety, "putting her in a position of peril".

The service is also accused of failing to provide adequate training on how to recognise the symptoms of psychiatric injury.

"The deceased did not receive any or proper monitoring of her condition while she continued to work in a stressful environment," the claim states.

The claim also alleges the police force had failed to devise a system for the flagging of police officers involved in numerous distressing or traumatic incidents.

As a result of its negligence, McDonald had suffered a major depressive disorder, chronic PTSD, alcohol abuse and death by suicide, it is alleged.

Mr McDonald said he now suffered from an adjustment disorder with depression and anxiety.

He was on track to become a superintendent, before he was medically retired.

He is claiming about $900,000 in future lost earnings, in addition to damages and interest. He is also seeking damages on behalf of his two children.

Damages are limited to $750,000 in the NSW District Court, but it does have the discretion to lift the cap.

In a statement to the ABC, the NSW police force said it could not comment specifically on the tragic circumstances which led to the death of a serving officer.

"NSW police continues to improve its practices and procedures, having made significant advances over many years to minimise the psychological impact of policing duties on our officers, who frequently undertake stressful and difficult work," the statement said.

"As a major priority, NSW police encourages the reporting of these impacts and offers a range of services to support, guide and educate our staff.

"These support services are comprehensive and effective.

"It is well understood that every officer's circumstances are unique and most often extremely complex with regard to the impacts of psychological injury."