IF Richard Slater hadn't consumed methamphetamine in the hours before he broke into a house at Hamilton and was subsequently chased, tackled and held in a "choke-hold" then it is "highly unlikely" he would have died, a forensic toxicologist and pharmacologist has told Newcastle Supreme Court.
Conjunct associate professor Dr Michael Kennedy provided an expert opinion for the prosecution in the trial of Benjamin Batterham, who is accused of murder over the death of Mr Slater, who broke into Mr Batterham's home on March 26, 2016.
Dr Kennedy told the jury his opinion was that Mr Slater suffered a cardiac arrest due to a methamphetamine-induced irregular heartbeat, which occurred in response to the sudden sprint from the home he had just broken into and the struggle with Mr Batterham.
And he said the cardiac arrest occurred against the background of Mr Slater's cardiomyopathy, or disease of the heart, which was also presumably methamphetamine-induced.
And later, during cross-examination, he went further than that, agreeing with another medical expert that methamphetamine alone could have caused Mr Slater's death and then agreeing with Mr Batterham's barrister, Winston Terracini, SC, that the methamphetamine alone, in fact, did cause Mr Slater's death.
"If he hadn't been taking methamphetamine and there was simply the fight, he probably wouldn't have died," Dr Kennedy said. "The fighting alone, no. The methamphetamine and the fight, yes. Methamphetamine was the agent in that it killed him rather than the fight alone."
And Dr Kennedy said he disagreed with the opinion of Dr Naren Gunja, who told the jury on Tuesday that Mr Slater died from asphyxiation and opined that the contribution methamphetamine toxicity had in causing Mr Slater's death was less significant.
"I don't think he had all the information before him," Dr Kennedy said of Dr Gunja.
Dr Kennedy said, on his view of the videos that recreated the struggle, it did not appear that the hold Mr Batterham had on Mr Slater would have obstructed both carotid arteries, major blood vessels in the neck that supply blood to the brain.
He said if both of Mr Slater's carotid arteries had been obstructed he would have "passed out almost immediately", but his heart would have kept beating.
Meanwhile, Paul O'Keefe, the man who was drinking with Mr Batterham at his home when Mr Slater broke in, described Mr Batterham as holding Mr Slater "in a headlock of some sort".
Mr O'Keefe denied kicking Mr Slater while he was on the ground, disputing the evidence of some witnesses.