A man who allegedly planned a terror attack on a Sydney police station after converting to Islam in jail was photographed several times showing a hand gesture connected to Islamic State, a court has heard.
Greg Ceissman is the first offender in the state targeted under powers allowing suspected radicalised inmates to be locked up beyond their sentence term or monitored in the community once released.
The state is seeking a three-year extended supervision order against the 24-year-old, who allegedly told someone he was planning to attack Marrickville Police Station and behead a police officer.
Ceissman, who is not charged with a terror offence, has denied being an extremist Muslim or having any terrorist allegiances.
He's separately been charged with failing to comply with interim supervision orders by browsing the internet on a phone with undeclared internet applications Facebook, Skype and WhatsApp
Middle East expert Rodger Shanahan in the NSW Supreme Court on Tuesday said several different photos in separate locations showed Ceissman giving a gesture associated with Islamic State (ISIS).
"The cumulative effect of that would indicate he's doing that for a specific reason," he said.
"Given the well-known nature of that symbol it would be reasonable to conclude ... he's doing it to show some affinity for Islamic State."
Under cross-examination by Ceissman's lawyer, he agreed the gesture had many connotations and wasn't universally used by ISIS supporters.
Psychologist Naomi Prince said Ceissman had actively deleted his internet use and call history.
She accepted under cross-examination that he may have wiped his web history because it included several entries for pages from a website called "F**kbook".
She also said Ceissman had been deceptive by lying to police about using Facebook, but agreed it could be for reasons other than supporting ISIS.
The hearing before Justice Stephen Rothman continues.