Trial begins for man accused of being 'lookout' for meetings before Curtis Cheng shot dead

Mustafa Dirani allegedly acted as "lookout" as two men met to exchange the gun later used by teenager Farhad Jabar to kill NSW Police accountant Curtis Cheng, his trial has heard.

Dirani, 24, appeared for the first day of his trial in the NSW District Court on Thursday charged with conspiring with others - including Raban Alou and Milad Atai - to do acts in preparation of a terrorist act or acts between August 6 and October 2, 2015.

In his opening address to the 12-person jury, crown prosecutor Paul McGuire SC alleged Dirani was the "counter-surveillance man" for meetings between Alou and Talal Alameddine.

He told the jury they "might well infer" one of these "highly illegal" events included the exchange of a .38 calibre Smith & Wesson revolver, later passed to Jabar - also known as Farhad Mohammad - and used to shoot Mr Cheng in the back of the head as he left work.

The prosecution alleged Dirani's "important role" as a co-conspirator also involved facilitating the meetings by driving behind Alou "effectively in a convoy".

AAP