"Mr Locke had turned away from you moments before the attack and what you should have done was to have walked away, but you did not do so.
"You formed a murderous intention and acted on it, using a knife you happened to be carrying."
Locke was vulnerable at the time of the attack, because he was stabbed from behind while sitting down.
The New Zealand man, who suffers from a blood clotting disorder, lost a lot of blood and could have died from his injuries without medical intervention, Justice Dixon said.
He is significantly affected by fear and anxiety when in public.
Byron pleaded not guilty to attempted murder and continues to deny he was responsible.
The court heard he had a traumatic childhood and was homeless by the age of 11.
Byron was sentenced to 12 years jail, with a nine-year non-parole period.
He has served almost 600 days in pre-sentence custody, where he is being held in tight security after assaults on prison officers.