But according to his family, Mr McGrath's life began to unravel long before he entered the factory on May 17 last year. His parents, Alan and Ann McGrath, claim he was subjected to relentless bullying in the "Soggies", which exacerbated his mental-health problems. The treatment of McGrath, who was just 20 years old when he joined the SOG, one of the youngest graduates to do so, raises significant concerns about the culture of the secretive taskforce and how its members deal with extreme pressure and shocking violence. When Mr McGrath left the SOG in 2008, he was suffering acute post-traumatic stress syndrome. He relied on a daily cocktail of antidepressants and antipsychotic medications, while codeine helped him cope with physical pain from injuries sustained on duty. He would later develop a dependency on codeine, a problem with alcohol and a taste for illicit drugs.

A father of two boys, Mr McGrath had visited psychiatrist Dr Peter Marriot weekly since 2007, including the day before his tragic death. Dean McGrath. "My mood varies from sadness to tears to anger. I experience flashbacks of bloodied, dead bodies. I feel anxious all the time. I suffer from headaches. I am hyper-vigilant. I feel naked without a gun. I have little enjoyment in life," Mr McGrath said in an affidavit to the Victorian Workcover Authority. He traced his mental health problems back to a siege in Hampton in August 2002, less than a year after he joined the elite taskforce often referred by other police as the "Sons of God". Waiting for instructions, he watched as a man killed his 10-week-old daughter by smashing her against a wall.

"I was at the front window of the flat and watched it happen." Vivid memories of the incident would haunt his dreams. "I saw the young girl who would now be a toddler in a white dress with red blotches. My wife said I was grinding my teeth heavily at night and I began to lose a fair amount of my hair," he said in the affidavit. In February 2005, Mr McGrath was involved in the mobile intercept of Wayne Joannou, who was wanted over the murder of a man in Sydenham the previous year. Joannou, sitting in a car parked in a South Melbourne street, levelled a shotgun at SOG officers and was met with a volley of gunfire.

"I remember seeing his bullet-riddled body with blood." A talented artist, Mr McGrath was asked to sketch the scene. He said part of a damaged window from Joannou's car was mounted at the SOG office as a grim souvenir of the mission. The officers involved also signed a front-page story from the Herald Sun that was put on display. A few months later, in April 2005, Mr McGrath was first through the door of the Brooklyn home of the notorious Chaouk family.

Mohamed Chaouk, 29, died when he was shot in the neck by another SOG member. "It was dark and men were yelling and torch lights moved rapidly. There were four loud shots above me and I thought I had been shot. A man had been shot dead at the top of the stairs by an SOG member. I felt sick, guilty, ashamed and distressed," Mr McGrath stated. He said formal debriefing sessions or counselling were rarely offered. Usually members would head to the nearest pub. Mr McGrath's growing reliance on alcohol had come to the attention of colleagues, who would place empty beer bottles and bottle tops in his locker. On another occasion, a .45 calibre bullet was also placed on the locker's top shelf. He failed an internal psychiatric examination, which was immediately spread among his colleagues and triggered further bullying and taunts.

He was called "Magoo" by workmates, who would shout: "Magoo, it's medication time." A self portrait by Mr McGrath. He claimed a senior-ranking officer would also sneak up and punch him from behind. "I can take pain, but sometimes my ribs would hurt for a couple of days, but I could not complain or (I would) face further ridicule," Mr McGrath stated. After filing a WorkCover claim in 2008, a superintendent and an inspector visited Mr McGrath at his home.

Increasingly paranoid, Mr McGrath covertly recorded the conversation, during which the senior officers conceded there were problems within the hyper-masculine ranks of the SOG. "They've got a jungle mentality, in all aspects they eat their own, that's their culture," one officer said to Mr McGrath and his wife. He was later found to have a permanent impairment of 50 per cent and received a significant ex-gratia payment from the force. Last week, the owner of the plumbing factory in Governor Road, David Grierson, 46, was acquitted by a Supreme Court jury of the attempted murder of Mr McGrath. The decision devastated his family and friends.

The charge had already been downgraded from murder after Justice Michael Croucher found the cause of Mr McGrath' s death could not be established. Mr Grierson had claimed he acted in self-defence, because Mr McGrath entered his plumbing factory armed with a sawn-off shotgun. He demanded drugs and money from Mr Grierson, before hitting him with the butt of the gun. Mr McGrath found drugs and money, but was not satisfied, the court was told. He put down the gun, picked up a 47-kilogram statue and walked towards Mr Grierson, before losing balance and stumbling.

"When he fell to the ground there was a loud thump," prosecutor Peter Chadwick said during his opening. David Grierson leaves the County Court last week. Credit:AAP Mr Grierson was alleged to have grabbed the gun and repeatedly struck the barrel on Mr McGrath's head and neck. The jury heard Mr Grierson ignored calls to stop, saying: "F--- him. You can't rob me. You can't do this to me." The gun used to bludgeon Mr McGrath was never recovered.

Jurors had to weigh up what caused Mr McGrath's death and could only find Mr Grierson guilty if they believed beyond reasonable doubt that he, and not the crushing blow of the statue, was to blame. Alan McGrath is bitterly disappointed with the police investigation. "The police never went to the factory. It took the killer to hand himself in before they entered and found Dean's lifeless body ... The homicide squad thanked us for causing a commotion otherwise they may have never recovered his body," Mr McGrath said. Ann McGrath said several convicted criminals had entered the factory in the hours after Mr McGrath's death and smoked the drug ice, while a small child related to one of the men was fed fish and chips. "They tied up his body, wrapped him in plastic and placed him into an airconditioning unit that was sealed at one end, and then they had a cement truck waiting on standby to dump him. Does this sound like self-defence?" Ms McGrath asked.