A former policeman has been released from prison after the Court of Appeal overturned his convictions on two charges, for punching a teenage boy and then perverting the course of justice.

Former Senior Constable Simon Mareangareu, 55, was sentenced to a year in jail in August last year, after County Court Judge Jeanette Morrish described the attack in 2014 as "disgraceful and utterly abhorrent".

Simon Mareangareu. Credit:Eddie Jim

Judge Morrish had said Mr Mareangareu "meted out summary justice" to Kyan Foster, then 16, and then prepared a brief of evidence to have the teen charged with offences he had not committed.

But on Tuesday, the Court of Appeal quashed the convictions, finding the judge had made prejudicial comments to the jury, the prosecution had introduced a new allegation after he closed his case, and the jury's verdicts were inconsistent on related charges.