Grant McLeod took a potentially lethal dose of cocaine before he went into respiratory and cardiac arrest on the second floor landing of the Chilkoot Trail Inn at around 7:30 on the morning of Aug. 30, 2008, an expert toxicologist told a coroner's inquest in Whitehorse today.

And he had just been wrestled to the ground and choked into submission by a police officer, the lawyer for McLeod's daughter reminded the six-person jury overseeing the inquest.

Toxicologist Dr. Walter Martz and forensic pathologist Dr. Charles Lee are the experts who determined McLeod's cause of death as a cocaine overdose.

However, lawyer Susan Roothman challenged their finding today, saying McLeod would not have died if RCMP officers had not struggled with him on the morning of his death.

Martz told the jury McLeod had 2.3 milligrams or cocaine for every litre of blood in his system, 10 times the amount a typical recreational cocaine user would show after getting high.

"Disregarding the circumstances, I have no doubt this killed the person,” he said of the drug.

However, he added, people who take cocaine regularly develop a tolerance for the drug and can survive a dose of more than twice what McLeod had in his system.

Even if they stop taking cocaine for a few weeks, they will still be able to go back and take amounts which might otherwise kill a person, he said.

"There is no limit .... Some people can tolerate high concentrations, some don't. It's unpredictable.”

He described the effects of cocaine on the human body and psyche as creating the "fight, flight or fright” stress reaction, even when there is nothing to run from.

"You feel like you have to escape some imaginary danger,” he said. "....The compound compels you to.”

He said the descriptions of McLeod's behaviour before police attempted to handcuff him, then wrestled him into submission, fit with Martz's observations of cocaine users.

Witnesses have said that on Aug. 30 of last year, McLeod was stumbling around the hotel lobby with a needle in his hand.

He was shaking and scratching his head and muttering about the Father, the Son and Holy Ghost, and he didn't acknowledge police commands, witnesses have testified.

The officers who were called to deal with him attempted to place him under arrest under the Mental Health Act.

When McLeod didn't co-operate, one of the officers tried to trip him to the ground, while another was behind him trying to subdue him with a choke hold.

McLeod went down with one officer on his back and another on his legs. The woman on his back had her arm around his throat throughout the struggle – which lasted several minutes – until back-up arrived and told her to release him.

He was unconscious by the time the officers put handcuffs on both his wrists. He never woke up.

Lee did an autopsy on McLeod's body four days later and found evidence of prolonged drug use throughout his body. His heart was weakened by scarring typical of cocaine users, and his lungs were spotted with crystals, residue from impurities in the street drug.

He also found bruising on McLeod's throat, broken blood vessels in his eyes and a fractured Adam's apple, injuries that were likely the result of being choked, the doctor concluded.

Roothman, the lawyer for McLeod's daughter, pressed Lee on whether the struggle with police would have pushed McLeod's already damaged heart and lungs past their breaking point, but Lee said the amount of cocaine in his system still could have killed the man on its own.

He said the officer would have had to keep choking McLeod for some time after he had passed out in order to actually kill him by strangulation.

The crystals in his lungs and the scarring on his heart alone could have killed him, the doctor said.

"That poses an increased risk of sudden death,” he said of the drug damage.

"Whether the altercation sped up his death is hard to say,” he concluded. "This is one of the problems dealing with these individuals. If you leave them, they may die on their own, if you restrain them in order to get them medical help then they are at risk of death.”

The inquiry is scheduled to wrap up tomorrow.