A NSW police prosecutor who told an undercover officer he fantasised about forcing parents to watch him rape their child was not being offensive, a court has heard.
Darryl Laurence Hahn faces two counts of using a carriage service to menace, harass or offend following conversations he had with a covert police operative using Skype chat and Manhunt, which bills itself as a "gay hookup site".
Hahn has agreed with the crown on some elements of the case but is fighting the charges.
The Downing Centre Local Court on Friday heard that during one conversation, initiated as part of a 2012 covert operation, Hahn said he favoured boys aged seven to 13.
In another, the court heard, he shared a fantasy that involved "tying up parents and raping their child in front of them".
"It would be fair to say that there could be no higher degree of offensiveness," prosecutor Jennifer Price said.
"It is at the highest end of the spectrum."
But defence counsel Doug Marr argued that an undercover officer posed as a willing and eager participant in the conversations and that Hahn never intended to offend him.
"If I send pornography to the church minister's wife, that's offensive and reasonable people would regard it as offensive," Mr Marr said.
"But if I send pornography to someone (who) says, `I enjoy looking at it, you know that I do, and if you've got any more' ... It's not the role of the state to vet or censor private communication between consenting adults."
He also said it was clear that Hahn was not referring to real sex acts.
"Whatever they're saying, it seems as if they're trying to be more disgusting or offensive than the other," he said.
"It's not as though it's real ... it's fantasy; role play."
Ms Price said the question of whether the undercover officer encouraged the conversation was less important because its subject was "objectively offensive".
Magistrate Lisa Stapleton said she considered it "a very important case" and had taken the rare decision of reserving her judgment so that she could put it in writing.
She will hand down a verdict when the matter returns to court on March 24.