Constable Alexander James Cox, 30, admitted showing pornographic videos of "doggy-style" sex to colleagues on two occasions, including to senior officers during a social getaway.
Cox said he claimed at the time the video was of himself for a joke and "just a bit of shenanigans", remembering the other officers laughing as he showed it to them.
"I just joked around and said it was myself," he told Sutherland Local Court.
"Everyone was just laughing, drinking. It was just a video from the internet."
Defence lawyer Paul McGirr said the case against Cox was "extremely weak". (Dean Lewins/AAP PHOTOS)
Several of the officers involved told the court they had taken Cox at his word that he was the one in the video and did not recall it being received as a joke.
Cox is facing one count of recording intimate images without consent and one count of distributing intimate images without consent, allegations he denies.
The charges do not relate to the video shown to senior officers but rather to footage allegedly depicting himself and a woman with whom he had a brief sexual relationship.
Cox is accused of showing that footage to two fellow police officers, Zachary Barrett and Sam Kirk.
Constable Barrett previously told the court Cox had shown them a short video during a workout session of a man and a woman having sex.
The woman was wearing a collar and lead, and Cox allegedly said it was him and his ex-girlfriend.
Cox's lawyer Paul McGirr said neither of the men could recall seeing the woman's "distinctive tattoos", which meant in all likelihood the video was not of her.
"This is an extremely weak case," he said.
"If it wasn't so serious it would be laughable. The only thing it falls on is the stupidity of Mr Cox."
The woman, who cannot be identified for legal reasons, earlier told the court she owned a collar and lead, and might have brought them to Cox's Engadine unit on one or more occasions to use during sex.
Cox claimed the couple had never used the collar and lead during intercourse, and that the woman might have mistaken them for a set of "silk ties" he bought that were merchandise from the movie 50 Shades of Grey.
An additional charge of distributing intimate images without consent against Cox was dropped by prosecutors after a key witness said an image she had allegedly been shown by him did not in fact contain a sexual act.
The detective in charge of the investigation, Sergeant Jason Savic, admitted potential "oversights", including failing to examine the complainant's phone or asking her to produce the collar and lead.
He said there were about 10 explicit videos saved on Cox's phone when it was seized by police, but none matched those detailed in the criminal complaints.
Magistrate Holly Kemp is due to deliver her decision on Thursday.
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