Brandon Trevor James Rich was living with his grandmother Denise at a home in the NSW town of Wellington when police paid him a fatal visit on 29 December, 2021.
Hours before he died, Ms Rich left the house after her grandson became verbally abusive.
His use of methamphetamine, commonly known as "ice", had led to numerous verbal arguments between the pair.
She left the home and returned with two police officers, telling them she wanted an apprehended violence order taken out against the young man.
Mr Rich initially agreed to go to the police station but changed his mind after being ordered to sit in the caged rear part of the paddy wagon.
After he ran back into the house, officers used their capsicum spray.
Tackled, hit twice with a baton and handcuffed, his face turned red and he told officers he couldn't breathe before foam came out of his mouth.
He died soon afterwards at Wellington Hospital.
In findings released on Thursday, Coroner Harriet Grahame found the 29-year-old died of an irregular heartbeat triggered by blocked arteries.
The physical exertion and stress from his struggle with police, as well as his morbid obesity, high blood pressure, heavy smoking and use of ice were all risk factors in the lead-up to his death.
Police had not followed standard domestic violence operating procedures requiring them to ask for further information, Ms Grahame said.
"(Neither) officer was in a position to assess the risk en route to the house because they did not know why they were asked to attend," she said.
Despite this, a decision to detain Mr Rich was made within minutes, escalating the situation, Ms Grahame said.
Officers also "did not clearly understand" their powers to detain Mr Rich.
They did not realise they should have given the 29-year-old a clear direction to either stay put or attend a police station and then allowed adequate time or opportunity to comply before detaining him.
"I remain particularly concerned about the evident confusion disclosed in relation to the direction given," the coroner said.
Other options to take Mr Rich to the police station were not properly explored and there was a "lack of strategic thinking" about how to calm the situation, she added.
In light of this, Ms Grahame recommended better de-escalation training for officers, saying this was likely "one of the most important issues" facing the police force.
In a statement delivered during the seven-day inquest in Dubbo, Mr Rich's mother Corina Rich described her son as a family man.
"I will always love my only son," she said.
"He showed me what the word 'love' means."
She said her family had been broken since his death and expressed disappointment that police had not offered their condolences.
"Brandon's life has been ripped away from us. He was very much alive before this incident."
A NSW Police spokesperson said the organisation would consider the findings.
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