An Auckland man who says he saw two youths sparring in the weeks before they allegedly murdered a man will give further evidence today at their trial.

Robert Watene testified yesterday at the High Court trial for the killing of dairy owner Arun Kumar.

Kumar was stabbed to death in what's alleged to have been an attempted robbery in June last year.

A 14-year-old is charged with his murder, a 13-year-old with manslaughter.

He reports he saw the two young defendants practicing closed fist movements, aiming at similar parts of the body to where Mr Kumar was stabbed.

But defence lawyer Julie-Anne Kincade claims CCTV footage shows no evidence of their play fighting, and that Watene made it up after being arrested for an unrelated incident.

Kumar's widow sobbed throughout much of her testimony in the High Court in Auckland yesterday.

The defence's cross-examination of a local man who knew one of the boys will continue this morning.

The Crown will then call a third youth who tagged along to the dairy on the day of the killing.