When Shelley LaDue's son Karl suddenly began staggering wildly around their home and screaming that he felt like he was on fire, she called 911 for help.

It was 9.30pm and Shelley had settled down for the night, but it soon became clear something was very wrong with her son.

"His eyes were blood red," she told 9news.com.au.

"He stumbled around like he had drunk a case of beer but he hadn't had one drop of alcohol."

Karl LaDue's mother Shelley describes him as a "gentle soul". (Supplied)

The LaDues' property in Oregon. (Supplied)

Karl was begging for help and took off running across the family's sprawling property in Talent, Oregon – a town of little more than 6000 people.

Shelley managed to drag Karl out of some razor-sharp blackberry vines he had fallen into but she was unable to control his erratic movements, and he soon fell through a porch railing.

Shelley and her husband Chris tried desperately to settle down their distressed son by giving him water and comforting him.

But Karl was tall and strong.

After struggling with his father, Karl broke free and again took off, running through a forested area onto a nearby residential street.

"I get to the road and oh my god, there was police cars everywhere and ambulances everywhere, they were chasing Karl," Shelley said.

"These police officers thought they were dealing with a thug and they were chasing him and Tasering him.

"They Tasered him about 24 times.

"And Karl took it and took it and took it and took it, he would pull those wires out of his back and keep running.

"They were kicking him and pulling his hair and trying to get the handcuffs on him."

Karl, in a state of aggravated delirium, was restrained by police but soon went into cardiac arrest and died on the way to hospital. He was 23.

Karl with his parents Chris and Shelley at his graduation from Brighton Grammar School in Melbourne in 2007. (Supplied)

The night Karl died was September 5, 2012.

The LaDues had been back in the US for less than two years after a lengthy stint living in Melbourne, where Karl attended Brighton Grammar School in the city's south-east.

The family's move from California to Melbourne then back to Oregon had left Karl feeling isolated.

He had depression and was diagnosed with mild schizophrenia.

"He wasn't a kid who would get drunk, he wasn't out carousing, he was going to school every day," Shelley said.

"He would have to deal with these voices every day and he dealt with them amazingly.

"He got his driver's licence. He was doing great."

It later emerged that in the hours before his death, Karl had travelled to a "headshop" – a store specialising in smoking paraphernalia - with a friend from his school days in Australia who was visiting.

The pair had been given a free sample of Bizarro, a smokeable synthetic cannabis product also known as "spice" and marketed as herbal incense to circumvent strict US drug regulations.

Spice is made by spraying plant matter with synthetic cannabinoids, which bind to the same receptors in the body as the active ingredients in cannabis.

Karl's friend said it had taken just 10 minutes after smoking a few puffs of the Bizarro for the first signs of his episode to begin.

Karl was diagnosed with mild schizophrenia in the years before his death. (Supplied)

Bizarro was marketed as "herbal incense" and marked as "not for human consumption" but was a popular, smokeable synthetic cannabis product. (Supplied)

'A GENTLE SOUL'

Karl loved video games, especially World of Warcraft.

At one point, he was the No.1 ranked player in the US and No.3 in the world at the massively popular online game.

He had taken up music and was playing drums in a hard rock band.

Karl's classmates from Brighton Grammar remembered him as a quiet student with an lively sense of humour.

"His acting teacher said he had a penchant for comedy and he had everything it took to apply to that industry," Shelley said.

"He was still testing a lot of waters.

"Then we moved from there.

"It's awful, it's god awful."

Karl was one of the world's top-ranked World of Warcraft players. (Supplied)

Karl in a Brighton Grammar School photo (left) and with his mother Shelley (right). (Supplied)

Karl's father Chris (left) is a scientist and inventor. (Supplied)

The death of Shelley and Chris's only child shattered the family.

For many years, Chris was unable to even look at a photo of his son.

But Shelley grieved differently.

"When he passed away, I wanted to celebrate his life," she said.

"I wanted to put posters of Karl's face all over town and I wanted a float and I wanted to have a big thing about who Karl was and say, 'This was my son and he's gone now'.

"I wanted to tell the whole world and have a party for Karl."

'IT WAS LIKE TORTURE'

As the shock of their loss subsided, the couple became consumed with questions.

Why had Karl, "a gentle soul", reacted the way he did? Why had the police Tasered their son so many times when paramedics were standing by ready to help?

With some reluctance, the couple lodged a lawsuit against the local police and fire departments, the responding officers, and Zencense - the company that made Bizarro.

Gruelling depositions meant the LaDues had to relive the night of their son's death over and over.

"There's no number (in compensation) that can help but what you have to do is make people accountable," Shelley said.

"I had to talk and I had to be deposed and oh my god, it was like torture for years.

"My mourning and my grief has been different than somebody else (whose loved one) got in a car accident and there's a funeral.

"Mine is a little different."

The LaDues settled their case out of court, but US authorities were also building their own separate brief of evidence against Zencense.

The company's operators were Benjamin Galecki and Charles Burton Ritchie, movie producers behind the star-studded documentary Misery is Comedy .

Galecki and Ritchie were sentenced to 28 and 32 years behind bars last year for their roles in running a US$21 million spice operation.

Court documents and statements from prosecutors revealed the company would regularly tweak the recipe for their products – sold under the names Neutronium, Orgazmo, and Sonic Zero in addition to Bizarro - and rename the key ingredients to stay one step ahead of regulators.

It was prosecutors' second attempt at jailing the pair after an earlier jury failed to reach a verdict.

But in a twist befitting one of their films, Galecki and Ritchie's convictions were soon vacated.

A court found their trial judge had erred in barring a US government scientist, who had been accused of soliciting a minor for sex, from testifying for the defence.

After much legal wrangling, Galecki and Ritchie's sentences were eventually reinstated but just last week, the pair launched a new round of appeals.

Their latest appeal remains before US courts.

For Shelley, helping eradicate what she calls the "poison" of spice and better training for first responders who deal with mentally ill young people are slivers of hope from the darkness of her personal tragedy.

But the thing that troubles her more than anything is not being able to see the man Karl would grow into.

"He was a sensitive person," Shelley said.

"He had a shy side to him, he had insecurities, like young people do.

"He was trying to find who is Karl. He was still trying to work out who am I?