A FIFO worker was suffering psychosis and believed he was working with ASIO to take out a paedophile when he attacked a mine site colleague who died during the assault, the WA Supreme Court has heard.
Troy Adam Hausler, 32, had initially been due to stand trial for the murder of Tobias Richter, 40, at the Pilbara Minerals' Pilgangoora site, south of Port Hedland, in November 2019.
But at the start of proceedings, last month, prosecutor Les Hobson said the state would accept Hausler's plea to the lesser charge of manslaughter, saying there was insufficient evidence to prove an intent to kill.
Hausler pleaded guilty to a downgraded charge of manslaughter over the death.
The court heard Hausler followed Mr Richter into a tunnel near a crusher where he was working with a high-pressure hose.
His defence lawyer, Rebekah Sleeth, said Hausler remembered following Mr Richter into the tunnel to confront him about his belief.
The court heard he grabbed him and they wrestled before falling to the ground.
Hausler then felt for Mr Richter's pulse, but did not find one.
He then wrapped Mr Richter's body in a tarpaulin and secured it with ropes.
Hausler left the scene, returning with a tray-backed four-wheel drive.
A coworker entered the area, saw the tarpaulin near the vehicle and found Mr Richter deceased.
Hausler then told the colleague "it's rubbish" and "it's shit, we have to get rid of it".
The worker left and returned with another colleague, and Hausler asked them for help loading the body onto the truck which they refused to do and called police.
Injuries found not to be cause of death
Mr Hobson said a coroner found DNA from Hausler on Mr Richter's neck and collar, and bruising to his head, neck, torso and limbs consistent with a "significant and substantial assault", albeit one which did not involve a weapon.
However, those injuries were not found to be the cause of death.
The coroner also noted widespread severe hardening of the arteries and indications of a previously unknown coronary condition.
The court was told the exact cause of death remained unknown.
Delusions about working with ASIO to 'deal with' Mr Richter
Ms Sleeth submitted evidence from two psychiatrists, with one finding evidence of schizophrenia or a schizo-affective disorder.
The second found symptoms consistent with bipolar with psychotic features.
The court heard Hausler believed his colleagues were with ASIO and were communicating with him telepathically, telling him to "deal with" Mr Richter.
Hausler believed Mr Richter was a paedophile and was going to harm his children, something that the court heard was entirely untrue and had no basis in reality.
The court heard be may have made Mr Richter the target of his delusion because he had been chatting to him, and Mr Richter had asked if he had kids, and whether he had pictures of them — something that in Hausler's own words was a perfectly normal thing that people do.
The court heard Hausler's presentation was atypical in that it had a late-onset and there were no indications of psychosis in his life until that point.
Ms Sleeth said Hausler managed to hide a lot of his symptoms for a long time.
He was "extremely ashamed" of having a mental illness and thought it to be a sign of weakness, Ms Sleeth said.
She said in reality Hausler thought of Mr Richter as a "hard-working man who was well respected by the company".
Family grieve loss of 'hardworking, brave' man
Mr Richter's sister, Vanessa Richter, read a victim impact statement to the court from her mother, who watched on from the public gallery.
"I am broken, numb, dead inside," she read.
She said the fact Hausler tried to dispose of her son's body compounded her grief.
"Tobias's kids will have to live knowing what was done to their dad," she said.
His sister, Vanessa, said she had suffered post-traumatic stress following her brother's death and had been forced to quit her job with WA Police.
Ms Richter broke down as she described losing her two-year-old daughter to cancer six months before police came to her door on November 11 to advise her of her brother's death.
"I don't know that I can ever really put into words what that felt like," she said.
"It felt like being punched in the chest and I couldn't breathe.
"(I knew) working in the mines could be dangerous, but no one would ever expect your brother to be killed by his supervisor."
A statement from his father was also read into the record, where he said he had raised Mr Richter to be respectful.
Mr Richter said his son had served in the armed forces and received a medal for bravery.
His partner, Toni, said Mr Richter had been a father to their two biological children but also his step children, and was close to his step-grandchildren.
She said all her children struggled with his death.
She described one of their sons, who also had complex needs, being so traumatised he slept in his father's clothes to comfort himself, and had difficulty coming to terms with the fact he was gone.
"He just wanted me to go to the airport and pick his daddy up," Toni said.
Toni is the sister of Hayley Dodd who was abducted and killed by Francis John Wark in 1999.
Moral culpability weighed in sentencing submissions
Ms Sleeth said Hausler's mother and wife, and two character witnesses were present in court to support him.
She said Hasuler was a man who has "never had an inclination towards violence in his life".
She said Hausler had grown up in Ballarat and had not completed high school but had completed extensive on-the-job training certificates.
She said his mother had described him as "quite (a) logical and practical man who enjoyed boating, fishing and making things with his hands" who was a "loving son".
Two school friends provided character witnesses, one of whom Ms Sleeth said found it a "great shock" to hear of the charge.
Ms Sleeth said when Hausler "came back in touch with reality" and realised what he had done, he became suicidal and didn't know how to live with himself, and his focus was on Richter's family and not himself.
She said his actions at the time had been described as "callous" however they were consistent with his delusion that Mr Richter was a bad man.
She also said he did not attempt to provide medical assistance but that there was no suggestion that it would have yielded any result.
However Mr Hobbs said "nobody will know if that (resuscitation) may have helped Mr Richter at that time".
Justice Joseph McGrath said the state had accepted Hausler was under a psychosis at that time and was substantially impaired in his judgement.
He noted this would go to his moral culpability at the time of the incident.
Hausler will return to the Supreme Court for sentencing on March 17.
