Paul Fennessy lay alone on the trampoline in his mother's backyard. It was a warm summer evening in Canberra and he wore a black singlet and pants. In his backpack was what had become of his life: toothpaste, deodorant, hair conditioner and a couple of packs of pharmaceutical drugs.​

"Can I stay, mum?" he asked when Ann Finlay returned home from work at the hospital. No, she replied. She could do no more, Paul's little sister had seen him like this too many times and Ann needed to get him help. "Can I come back tomorrow?"

"Yes. Of course."

It was January 6, 2010, and Paul had overdosed on prescription opioids once already that day. Ann begged the hospital to keep him there after he was revived by paramedics. He had nowhere to go, no phone and access to so much medicine. She had found the empty packets under his bed months ago but her tireless entreaties to his doctor and pharmacies did not stem the flow. Hours later, just blocks away; Paul would be found, crouched by a suburban fence, having finally succumbed to the addiction. He was 21.

Of 668 opioid-related accidental deaths in Australia in 2013, 70 per cent, or 470 were due to pharmaceutical opioids, the most accurate available figures from the National Drug and Alcohol Research Centre show. Many of those deaths involved oxycodone, a common opiate, the misuse of which, Australian Institute of Health and Welfare figures show, grew 67 per cent from 2010-11 to 2014-15.

In the US, where hundreds are dying a day on both legal and illegal opioids, it's been called an epidemic. Australian experts say it is a preview of what is to come.

For Paul, it started in his early teens with diagnoses of anxiety, depression and social phobia. He was prescribed anti-depressants, anti-psychotics and opioids to help deal with his emerging problems. Paul learned quickly that he could access massive amounts of prescription medication by doctor-shopping - moving from one GP to the next to obtain the drugs.

Between December 2007 and his death on that day in January 2010, Medicare records show, Paul filled more than 150 such prescriptions from 18 different doctors and 18 chemists across Canberra. "He was very creative to go in and spin a yarn, for somebody that was so shy," his aunt Mary Finlay says.

On the day he died, not one of the seven drugs in Paul's body was illegal. But it was a highly toxic mix of prescription opioids, anti-psychotics and anti-depressants - an all too common combination seen in coronial reports.

Just hours after his mother came home that night, his body would be found. On the inside of his left wrist, a tattoo read: 'Made in Ireland'. Ink that spoke of his ancestry and birthplace, but equally to a troubled young man's search for belonging.

Paul was four years old when he emigrated to Australia with his parents. They settled first in Alice Springs, but then his parents divorced, and his father returned to Ireland. Paul and Ann moved to Canberra, though she knew he missed his dad. Paul developed obsessions; with dinosaurs, the Titanic, volcanoes and the cello. A shy child, he would make perfume with flowers. At school, he struggled to make friends.

Ann remembers this conversation with her son. "He had said, 'I'm a bit different from other people mum, aren't I?' and I said, 'It's great though isn't it, that you have different interests than other people, it's interesting.'"

In his early teens, Paul was diagnosed with social phobia, anxiety and depression. Someone gave him a bottle of vodka at 16 and Ann saw a change in him. When he was 17, Paul completed a program at Ted Noffs for alcohol misuse. When he finished year 12 he got an apprenticeship at David Jones.

Paul was funny, two of his closest friends after school, Emma Green and Chantelle Milin, said. An immaculate, suave and sensitive young man, who Emma described as "almost too magical to be on this earth". But one day in March 2008, their friendship would be severed as his addiction and mental health troubles exploded.

That day, Paul sent out a text, saying he wanted to end it all. Emma and Chantelle found him on the trampoline, drowsy from too many sleeping pills but refusing to go to hospital. At a loss, the pair drove him to the Rivett shops and tried to get him to eat, until Emma called the police to help, the patrol cars came screeching up and bundled a compliant Paul inside and took him to hospital.

The admission that March afternoon, though his friends did not know it, was his third drug-related trip to hospital in less than six months. The next year of his life was punctuated by more admissions, overdoses; possible attempts. His mother, aunt and uncle would scratch their heads, wondering why every admission was dealt with in isolation, his earlier mental health diagnoses seemingly forgotten. "They'd deal with that and then send him on his way again," his uncle Philip Hillsdon says. "There was no connection then with the mental health unit and drug and alcohol unit to say this young fellow's done it again, we need to take him seriously."

Paul was trapped in a common cycle, consuming dangerous combinations of substances with complex interactions, Victorian Institute of Forensic Medicine's David Ranson says.

Paul, Dr Ranson says, was "in a different spectrum of drug harm".