A Queensland man sentenced to life in prison for fatally stabbing a drunk German backpacker has had his conviction overturned on appeal.

Jamie Douglas Saxon, 36, was found guilty of murder in October after he knifed Dominik Schulze during a Brisbane road-rage incident two years earlier.

The 30-year-old – who was in Australia on a working holiday – was skylarking on an inner-city road after a night of drinking when the men clashed.

Mr Schulze had his pants down and was waving his genitalia about when he was “clipped” by a car driven by Saxon’s girlfriend, Jessica Wilkes.

Angry at being bowled over, he called Saxon names, was abusive and “clearly wanted to fight” his original trial was told.

He also pushed Ms Wilkes and attempted to throw punches but they didn’t connect because he was so drunk.

It was alleged at the trial that Saxon then took a long, sharp fishing knife from the car and stabbed Mr Schulze up to four times.

Mr Schulze’s injuries were so bad that “intestines were protruding from his stomach”.

He was rushed to hospital about 4am but by 12pm that day he had died.

Saxon did not deny stabbing Mr Schulze but pleaded not guilty murder saying he had acted in self-defence.

His conviction was quashed on Monday and a retrial ordered after the Court of Appeal heard the jury had been misdirected during the trial.

A document given to it contained an incorrect paragraph saying that the self-defence argument could be excluded under certain conditions.

Crown prosecutor Mark Green conceded this was an error but said it did not matter because the trial judge had made other directions rendering the incorrect information irrelevant.

A full bench of the court disagreed. Saxon will be retried at a date to be fixed.