Surveillance footage of a number of New South Wales and Queensland police officers allegedly consuming hash cookies has been shown in a Sydney court.

The footage was tendered as evidence in the case against former Tweed Heads detective Shane Diehm, arising from a weekend away on the Gold Coast with serving and former police officers in August 2010.

Diehm was discharged from the force after pleading guilty to two counts of lying to the Police Integrity Commission (PIC) about his own drug use.

He returned to court to fight a further two charges related to lying about witnessing other officers using illegal substances.

Sydney's Downing Centre Local Court was shown police surveillance footage of the group, including Diehm, allegedly eating hash cookies and discussing how long the drugs stayed in a person's system.

Diehm claimed he remembered nothing of the weekend, because of depression, post-traumatic stress disorder and binge drinking.

However, the Crown alleged he did and that he had a "clear and obvious reason to lie" to protect his friends.

Diehm said he was not trying to protect anyone.

He broke down crying in court and spoke about how he had let down his parents and son.

He told the court he came clean to the PIC despite the dire consequences it would have on his career.

The hearing continues.