A Darwin security guard has been found guilty of unlawfully causing serious harm to a US marine by striking him outside a nightclub.
The jury took just over four hours to reach a unanimous verdict in the Northern Territory Supreme Court.
Hayden Summers, 34, had pleaded not guilty to one charge of unlawfully causing serious harm, along with an alternative charge of negligently causing serious harm, relying on arguments of self-defence.
The incident happened in the early hours of April 11 last year after US marine Glen Thomason was ejected from Monsoons nightclub in the city's bar district.
During the trial, the court heard Mr Thomason's injuries led to him spending a "significant amount of time" in hospital and then rehabilitation after having part of his skull removed.
The jury members examined CCTV footage of the interaction between the two men, which had no recorded audio.
They also heard evidence from nearby witnesses about what was said.
"Unusually in this case we have most of the witnesses — who were bouncers — who were sober," Justice Jenny Blokland said in her summing-up of the case for the jury on Thursday afternoon.
"I have to tell you that's very unusual in a Darwin case emanating from Mitchell Street."
During her summary of the evidence, Justice Blokland said "clearly Mr Thomason was disgruntled at his rejection" and he had not been told why he was removed from the nightclub.
According to some witnesses, Mr Thomason was heard saying, "I could kill you, I'm a marine," or words to that effect, she said.
Mr Summers gave evidence that Mr Thomason's hand gestures were threatening, while the Crown argued he was just trying to explain how he had been "manhandled" by another security guard.
Justice Blokland told the jury it was unclear if it was the strike to Mr Thomason's head or hitting the road that knocked him unconscious and caused the injuries, and by what degree.
Jury members were asked to consider if there was a reasonable possibility Mr Summers had acted in self-defence.
Justice Blokland reminded the jury of arguments from Crown prosecutor Ian Rowbottom that the strike to the side of Mr Thomason's head was not a reasonable response.
He argued Mr Summers failed to explore options other than "knocking someone out", including moving backwards, asking colleagues for help or just pushing Mr Thomason away.
Mr Rowbottom described evidence about threatening gestures as "a lie" that did not match the CCTV footage and he told the jury Mr Thomason "did not deserve a blow like that", Justice Blokland said.
The jury was reminded of Mr Summers's evidence that he was "an experienced crowd controller" who had worked for 15 years in the industry and was the head of security at Monsoons nightclub.
Mr Summers gave evidence that he was trying to de-escalate the situation and had told Mr Thomason to "calm down".
Justice Blokland said his evidence was that the strength of his hit was about "a six out of 10" and he did not mean to hurt Mr Thomason.
His evidence was that he feared Mr Thomason was about to punch him because of his hand gestures and a "death stare", Justice Blokland said.
Mr Summer's barrister Peter Maley had argued: "The slap was not unreasonable, it's not as though he used a knife or a kick in the head."
Outside court, Mr Summers's father said he was "disappointed" with the verdict.
A sentencing hearing will begin on September 8.
