Mustafa Dirani, 24, has pleaded not guilty to 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 - the day NSW Police accountant Curtis Cheng was shot and killed by Farhad Jabar.

Crown prosecutor Paul McGuire SC continued his opening address in the NSW Supreme Court on Friday for day two of the trial.

He told the 12-person jury Dirani had a closed chat group with Alou and Atai on the mobile application WhatsApp titled "Bricks" and bearing the black-and-white ISIS flag as its icon, which featured the "seal of Muhammad" insignia.

"At relevant times, the conspirators had beliefs in common that related to their interpretation of the Islamic religion and their support for the terrorist organisation Islamic State," Mr McGuire said.

"The common views expressed by the conspirators in this case not only refer to jihad and martyrdom but, relevantly and tragically for Mr Cheng and his family, referred to the justification religiously ... of killing kafirs."

Kafir means a non-believer, disbeliever or an infidel, he added.

On Thursday, the prosecution alleged Dirani had acted as the "counter-surveillance man" when Alou had "highly illegal" meetings with Talal Alameddine, who supplied the fatal firearm.

Mr McGuire said the jury may infer one of these events included the exchange of a .38 calibre Smith & Wesson revolver, later passed by Alou to 15-year-old Jabar and used to kill Mr Cheng as he left work.

Mark Tedeschi QC is representing Dirani and is expected to give his opening address for the defence when the trial resumes on Tuesday.

Australian Associated Press