Jack Pethybridge, 22, was found guilty by a District Court jury in January of orally raping and indecently assaulting a man after some late-night drinks at his parents' Barden Ridge home in July 2017.

But after a review of the evidence, the Court of Criminal Appeal said both verdicts were unreasonable.

Mr Pethybridge had maintained the incident in his bed was consensual and lasted minutes.

In contrast, the complainant told the trial he said "Jack, no. Stop, Jack. Think about (your boyfriend)".

Within seconds of the oral sex beginning, he used both hands to shove Mr Pethybridge's head away, the complainant said

The jury also heard from a woman who had been sleeping between the men before Mr Pethybridge climbed over her to perform oral sex.

She recalled hearing the complainant say "Think about (your boyfriend)" or "What about (your boyfriend)?" but did not sense the shove.

That and other evidence she gave was "difficult to reconcile with the complainant's case", Justice Mark Leeming said in reasons published on Tuesday.

The judge, whose decision was supported by Justice Julia Lonergan and Acting Justice Peter Hidden, said the jury should have entertained reasonable doubts.

"When assessed in the light of all of the evidence, there must be serious doubts that the complainant's evidence ... is correct," Justice Leeming said.

"Those doubts are not resolved by any of the other evidence at trial."

Justice Leeming also had doubts after considering contemporary messages including those between the complainant and his partner.

He noted the court's power to quash a conviction should be exercised with great care and it was "quintessentially a task for the jury" to determine whether they believed the complainant or Mr Pethybridge.

"But that task did not involve merely watching each man give evidence," he said.

"The jury was required to assess each man's evidence in light of the entirety of the evidence adduced at trial."

Mr Pethybridge served no time in jail between his conviction and acquittal as his sentencing judge bailed him pending the appeal.

Australian Associated Press