A 23-year-old man has been charged with refusing to answer questions over the murder of NSW Police Force employee Curtis Cheng.

The 23-year-old, believed to be Merrylands man Talal Alameddine, is currently in Goulburn jail.

Police on Thursday charged him with 20 counts of refusing to answer NSW Crime Commission questions in relation to the murder of Mr Cheng outside Parramatta Police Headquarters on October 2, 2015.

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Alameddine is already facing other charges in relation to the murder of the police accountant.

Police have alleged he supplied a .38 Smith & Wesson revolver to Raban Alou on October 2, 2015, which is the gun believed to have been used by 15-year-old Farhad Jabar to fatally shoot Mr Cheng.

It has also been alleged in court documents that on October 7, 2015, Alameddine damaged and secreted a mobile handset and SIM card to hide the evidence of a serious offence allegedly committed by Alou and Jabar and another.

Alameddine is currently in custody at Bowral Police Station and is expected to face Goulburn Local Court later on Friday.

He was due to face court in Parramatta on April 7 on the weapons charges.

His lawyer Stephen Zahr was told during his last court appearance that he should be prepared to enter a plea on that date.