BENJAMIN Batterham must be acquitted of both murder and manslaughter over the death of Richard Slater, who broke into Mr Batterham's Hamilton home in 2016, because the expert medical evidence has not established with any certainty the primary cause of Mr Slater's death, Newcastle Supreme Court has heard.
And during his closing address on Friday, Mr Batterham's barrister, Winston Terracini, SC, told the jury that the expert evidence - including a number of doctors and professors called by the prosecution - had not established beyond reasonable doubt that any act committed by Mr Batterham "substantially or significantly" caused the death of Mr Slater.
Mr Batterham found Mr Slater inside his home in Cleary Street on March 26, 2016, and chased him 330 metres before tackling him to the ground where witnesses say he held Mr Slater in a "choke-hold" and punched him in the head.
Mr Slater had a "potentially lethal" level of methamphetamine in his system, pre-existing heart disease and obesity and his cause of death has been the central issue during Mr Batterham's two-week murder trial.
Mr Batterham had a lawful right to chase and restrain Mr Slater and in order for a jury to convict him of murder, the prosecution must prove beyond reasonable doubt that an act perpetrated by Mr Batterham "significantly or substantially contributed" to the death of Mr Slater.
"The accused caused or substantially contributed to the death of Richard Slater by the application of pressure to his neck and downward pressure to his upper body while Richard Slater was in a prone position," Crown prosecutor Wayne Creasey told the jury during his closing address.
But Mr Terracini said even the prosecution's "star" witness, forensic pathologist Dr Jane Vuletic, was unable to give a definitive opinion as to Mr Slater's cause of death.
Dr Vuletic told the jury there was a number of factors that could have caused or operated together to cause Mr Slater's death, including being placed in a "choke-hold", the high level of methamphetamine in his system, his pre-existing cardiac disease and obesity.
But Dr Vuletic said the methamphetamine reading - which the jury heard was at a level "associated with death" - in combination with the pre-existing heart condition was the most likely cause of Mr Slater's death.
"If the major witness for the prosecution cannot give an opinion as to cause of death then you have in effect nowhere to go," Mr Terracini told the jury. "The verdicts must be not guilty of murder and not guilty of manslaughter. Based upon the evidence before you it is a one-way street."
The other medical experts are split over the exact cause of Mr Slater's death and the significance that any "choke-hold" had on triggering three episodes of cardiac arrest, with clinical toxicologist Dr Naren Gunja the only expert who opined that asphyxiation caused Mr Slater's death.
Mr Terracini summarised the insufficiency of the evidence relating to Mr Slater's cause of death with the answer to what he said was the most important question in the case; the cause of death may not have been any of the reasons that the medical experts have examined.
If they do clear the hurdle relating to Mr Slater's cause of death, the prosecution must then prove beyond reasonable doubt that Mr Batterham intended to either kill Mr Slater or cause him really serious injury.
On that front, Mr Creasey relied upon the evidence of witnesses in Cleary Street to submit that Mr Batterham went "completely over the top" from what was a lawful right to chase and restrain Mr Slater to an assault during which he choked and punched the intruder and ignored pleas to let him up.
Mr Creasey said if the jury could not be satisfied that Mr Batterham had the requisite intent to convict him of murder, then they could find him guilty of manslaughter on the basis Mr Batterham committed an "unlawful or dangerous" act when struggling with Mr Slater.