Two policemen deleted video footage from a teenage boy's mobile phone showing one of the officers assaulting the boy's friend, a trial has heard.

Simon Mareangareu. Credit:Eddie Jim

A County Court jury was on Thursday shown footage that Stuart Laird, then 17, recorded of policeman Simon Mareangareu throwing a punch at his friend Kyan Foster. The incident took place about 2am on Christmas Day 2014 at a Vermont intersection.

At the start of the video, Mr Mareangareu tells Mr Foster, aged 16 at the time, not to be smart. As the teenager spells his name, the policeman asks: "One name? Is that one name?"

Moments later, someone says "smartarse" and Mr Mareangareu throws a punch at the boy. Prosecutors told the court the punch left the teen with a badly bloodied nose.