Senior constable Christopher Charles Fullick, 37, had raised the defence of "automatism" as a result of post-traumatic amnesia, claiming he had no memory of the incident, or the next 10 minutes, after he was involved in a crash with the fleeing vehicle that "nearly killed" him.

Police in-car video captured the pursuit through the suburb of Hamilton, the near-fatal crash and then Mr Fullick sprinting from his vehicle and assaulting the driver, Anthony Kirk, 29, as he was being restrained by other police officers about 11pm on January 27 last year.

After a lengthy investigation, Mr Fullick was charged with assault occasioning actual bodily harm and common assault.

But on the second day of a hearing in Newcastle Local Court on Friday, and at the conclusion of the prosecution case, Magistrate Andrew Eckhold acquitted Mr Fullick of both charges.

Mr Fullick's defence team of barristers Paul Rosser, QC, and Michael Weightman, and solicitor Stuart Gray had provided expert evidence from a neurosurgeon, a neurologist and a psychologist who opined that the police officer was acting as an "automaton" at the time of the assault. The prosecution called psychiatrist Dr Jonathan Adams, who couldn't rule out the possibility that Mr Fullick was in an automatistic state at the time.

That became the crucial part of the case, with Mr Eckhold dismissing the charges because the prosecution had failed to "negatise" the defence of automatism.

During the first day of the hearing, Magistrate Eckhold was shown in-car video from another pursuing police car that was behind Mr Kirk as he sped away from police on January 27 last year.

After travelling through a number of Newcastle suburbs, the video shows Mr Kirk's car heading west on Veda Street before he turns right into Samdon Street, speeds through a give way sign at Denison Street and then careers into the intersection of Belford Street.

At the exact moment, Mr Fullick's police car flashes into screen heading west on Belford Street and the two cars collide, sending the fleeing vehicle spinning out-of-control before it comes to rest on the footpath out the front of the Hamilton Car Centre. The estimated speed of Mr Kirk's car was 85km/h, the court heard, as he hurtled through a red light on a blind corner and was milliseconds from killing himself, his passenger or those in the police car he collided with.

Police then swarm into the screen, attempting to grab the driver and passengers out of the vehicle.

A few seconds later Mr Fullick can be seen sprinting into shot, landing a kick on the driver before bending down and appearing to throw a few punches at the man.

"There is a kick, three punches and a stomp," Mr Fullick's barrister, Paul Rosser, QC, told Mr Eckhold.

The police-in car video meant the assault itself was not in dispute, and instead it was a question of whether "automatism" was demonstrated or not.

And after initially saying the hearing would run for four days, Mr Eckhold was left with no doubt that the defence of automatism could not be excluded after hearing just the prosecution case.

After the decision, Mr Gray said the defence had served on the prosecution a large amount of evidence that suggested Mr Fullick was not culpable.

"The defence served a comprehensive series of expert opinions on the prosecution to the effect that Mr Fullick was acting as an automaton while suffering from post-traumatic amnesia," Mr Gray said.

"Ultimately, the magistrate found the prosecution could not negatise this."

Automatism is a rarely used criminal defence and is concerned with involuntariness as opposed to any question of mental illness.

Unless the Crown proves beyond reasonable doubt that the act of the accused was subject to the control and direction of his will, then he must be acquitted because no offence has been committed, the law states.

The defence has applied for costs in the matter, with a hearing to be held in June.

Mr Fullick had been suspended with pay pending the outcome of the legal proceedings.

Newcastle Herald