The Brisbane Supreme Court jury returned its verdict on Thursday after deliberating for nine hours following a four-day trial on the count of murder with an alternative charge of manslaughter.
The 18-year-old man, who cannot be named as he was aged 17 at the time, followed David George Connolly, 43, as he left a shopping centre car park in Wilston in Brisbane's inner north just after midnight on January 22, 2023.
Following a brief confrontation that was captured in audio form by a security camera, the youth stabbed Mr Connolly once, resulting in a 15cm-deep wound to the side of his chest below the armpit that caused major damage to his lung and death within minutes.
The youth was arrested by police for possession of a knife in public soon after he stabbed Mr Connolly but 30 minutes before the victim's body was discovered lying on a footpath by passers-by at 1.45am.
The youth took the stand during his trial and gave evidence that he acted in self-defence when Mr Connolly started repeatedly punching him.
During his closing statement, crown prosecutor Michael Gawrych told the jury the youth's claim about being attacked was contradicted by a lack of injuries to Mr Connolly's hands and no injuries on the defendant's body.
"It's a complete fabrication, clearly designed by (the youth) to retrospectively justify the killing of an unarmed man," Mr Gawrych said in closing.
The jury members were previously instructed by Justice Michael Copley they had to reach a unanimous decision to return a guilty verdict on the murder charge.
The youth held his face in his hands after the verdict of not guilty to murder but guilty to manslaughter was read out.
Justice Copley remanded the youth in custody and adjourned the matter to a date to be fixed so a pre-sentence report could be prepared.
