High-profile NSW police detective Gary Jubelin is due to face a Sydney court today over allegations he conducted illegal surveillance.
Mr Jubelin worked on the investigation into the disappearance of three Aboriginal children - Evelyn Greenup, Clinton Speedy-Duroux and Colleen Walker - in Bowraville in the 1990s.
More recently, Mr Jubelin supported the families of the victims who in March sought a retrial application in the High Court based on failings in the criminal justice system's initial response to the suspected murders of the children.
The detective chief inspector was also the lead investigator in the fresh search for missing three-year-old William Tyrrell until taken off the case earlier this year during misconduct investigations.
Mr Jubelin's lawyer Margaret Cunneen has said her client denies "any wrongdoing whatsoever and will strongly defend the charges against him".
NSW Police in June charged the detective chief inspector with four offences under the surveillance devices act.
The professional standards investigation began after multiple complaints and was overseen by the Law Enforcement Conduct Commission, police say.
The allegations relate to recordings made at undisclosed locations in Parramatta and Kendall, the mid-north coast town where three-year-old William vanished in 2014.
In addition to the Bowraville investigation and leading the fresh search for William Tyrell, Mr Jubelin was involved in investigating the death of Sydney man Matthew Leveson.