Murdoch said Dunn whacked Wharawhara, causing him to fall backwards off the park seat, then kicked him around the head.
Dunn and a friend then left Wharawhara on the ground to go to K Rd.
A post mortem found Wharawhara died of blunt force trauma to the head.
Murdoch said the Crown alleges this was as a result of the assault.
But defence lawyer Sam Wimsett said Dunn was acting in self defence because Wharawhara attacked the defendant first and when Dunn left the park, Wharawhara was still alive.
The case wrapped up on Friday afternoon and the jury retired at 1pm to deliberate. They returned at 8pm with the guilty verdict.
Sentencing is set down for next month.