Former detective Roger Rogerson has told the NSW Supreme Court he believes he is a victim and took part in the disposal of a body only because he was helping out a mate.

The 75-year-old said his decision to help his friend, Glen McNamara, had "complicated" his situation and in hindsight he wished he had called the police.

Former detective Roger Rogerson leaves King Street court on Monday. Credit:Michele Mossop

Mr Rogerson and Mr McNamara are on trial for the murder of university student Jamie Gao.