Wegener appealed his conviction in April 2024 with his barrister Andrew Hoare arguing the prosecution was unfairly allowed to suggest his client was a drug user who had a close association with a drug dealer.

In a judgment handed down on Friday, Justice David Boddice accepted the jury was told of claims about Wegener's character that had nothing to do with his alleged actions involving Mr Suttie or his intention at the time.

"Contrary to the prosecutor’s contentions, his address was a direct attack on the appellant’s character," Justice Boddice stated.

The original trial heard Wegener responded aggressively to a greeting from the 37-year-old Mr Suttie as their respective groups passed in a park south of Brisbane in August 2018.

The late-night encounter at Woodridge quickly escalated and Wegener allegedly produced a knife with "scalpel-like" sharpness, slashing at Mr Suttie's face and then throat.

Mr Suttie's life support was turned off days later due to multiple organ failure caused by severe blood loss.

At the April appeal hearing, Mr Hoare said Wegener did not receive a fair trial as the prosecution had improperly told the jury he had a bad character.

"An association with a drug user and a drug dealer, both of which, the second clearly, imply the commission of serious crimes," Mr Hoare said.

He said the prosecutor at trial had no justification to cross-examine Wegener about his relationship with a known drug dealer.

Crown prosecutor Mark Green told the appeal hearing the drug dealer association did not affect the trial's outcome as the jury had accepted eyewitness and forensic evidence that Mr Suttie was allegedly slashed multiple times.