Two former detectives charged with murder have formally entered pleas of not guilty during a Supreme Court arraignment hearing.

Former police officers Glen McNamara and Roger Rogerson have been charged with the murder of 20-year-old student Jamie Gao in May last year.

The two men today entered not guilty pleas to the murder charge, as well as drugs supply charges.

Their trial will begin in July and is expected to last eight weeks.

Police have alleged the pair lured the younger man to a storage unit in Sydney's south-west, with Mr Gao attending the meeting carrying almost three kilograms of the drug ice.

Officers said the trio were spotted on CCTV entering the storage unit. Ten minutes later, cameras allegedly captured McNamara and Rogerson leaving, dragging a surfboard bag.

Mr Gao's body was found floating in waters off southern Sydney six days later.