Francois Joseph Ghassibe was in the back of a taxi on West Terrace in Adelaide when his driver was cut off by 70-year-old Brian Richardson on April 1, 2022.
When Ghassibe tried to break up a confrontation between the taxi driver and Mr Richardson, who had left their cars in the middle of traffic, Mr Richardson started pushing and punching him.
Ghassibe, who was 40 years Mr Richardson's junior at the time and 10 centimetres taller, retaliated with devastating effect.
As Mr Richardson's wife, brother and sister-in-law watched on from their car, Ghassibe - who later told police he had a background in martial arts - launched several blows at the older man before delivering a final, terminal kick to the chin, causing him to fall backwards and hit his head on the bitumen.
A post-mortem examination found the impact of his head on the roadway to be the killing blow.
Ghassibe climbed back into the taxi and left while bystanders rushed to Mr Richardson's aid.
He was later pronounced dead by paramedics.
Ghassibe pleaded guilty to manslaughter but denied that he murdered Mr Richardson.
While there was no question that Ghassibe's actions led to Mr Richardson's death, SA Supreme Court Justice David Peek was not satisfied beyond reasonable doubt that he intended to kill him.
"I find that the accused, in delivering the flurry of blows and then the kick, intended to put the deceased to the ground forcefully," Justice Peek said in his written verdict on Friday.
"However, I am simply not satisfied beyond reasonable doubt that, at the time of administering the flurry of blows or the kick, the accused possessed the specific intent to kill or inflict grievous bodily harm required for the crime of murder to be established."
Justice Peek did find Ghassibe guilty of manslaughter, satisfied that the kick was not in self-defence and therefore unlawful, that it was a dangerous act and that he should have realised it risked causing Mr Richardson serious injury.
The judge agreed with the defence proposition that, at the crucial moment in the altercation, Ghassibe was influenced by stress caused by "the unexpected and surprisingly aggressive conduct of the deceased".
His mental state was exacerbated by the cocaine and alcohol circulating through his bloodstream and the temporary impairment of vision to his only good eye from being punched and spat at, he found.
"You have taken my husband who I adore and will always treasure," Mr Richardson's wife, Michelle, told Ghassibe in a statement read out by crown prosecutor Lisa Dunlop.
"One day you will have to meet your maker and give an account of what you have done, whether you believe in God or not.
"I would not like to be in your shoes."
Ghassibe wiped away tears as he hung his head in the dock.
"I am so sorry that I've caused your family and friends this pain," he said.
"But sorry is only a word which is probably meaningless compared to the pain you now carry with you.
"You did not deserve to suffer like this at all and you have my sincerest apologies."
Ghassibe will be sentenced on October 16
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