A disgraced policeman will spend a year in jail after punching a teenage boy and then perverting the course of justice by having the teen falsely charged with assaulting police and resisting arrest.

County Court Judge Jeanette Morrish said the conduct of Senior Constable Simon Mareangareu was "disgraceful and utterly abhorrent" but conceded she had "agonised'' over her decision to impose a custodial sentence.

Senior Constable Simon Mareangareu. Credit:Eddie Jim

Judge Morrish said Mareangareu had "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.

Mr Foster told The Age that the case was "mostly about an abuse of power and then attempts to legitimise those false accusations against myself and my friend".