Crown lawyers have rejected the Defence's main argument - in the last days of the murder trial of a Dunedin doctor

Venod Skantha denies killing 16-year-old Amber-Rose Rush.

The Defence previously argued the Crown's key witness - a teenage friend of Skantha - was the real killer.

But Crown lawyer Robin Bates says there's no way the teen was responsible.

He says the boy would've had to be both a criminal mastermind - and a magician who could pull a knife out of nowhere.