The trial of two former Australian Defence Force Academy cadets for filming having sex with women cadets, and broadcasting it over chat service Skype started on Monday with the two pleading not guilty to charges of using a carriage service in an offensive manner.

However, the case could possibly be weakened since the question of if the women were aware they were being filmed secretly by Daniel McDonald, 21, or not came up. The Australian reports he insisted that the female cadet, called Kate, knew she was being filmed and broadcast and even waved to the camera.

The live sex show was streamed to Dylan Deblaquiere, 20, who was watching the steamy scenes with five other cadets in his room in March 2011. Mr Deblaquiere also filed a not guilty plea.

The bases of their pleas are the female cadet's testimony that her arrangement with the two is that they are friends with benefits or sex buddies. Her deal, however, includes several conditions such as the arrangement being kept a secret.

He was also supposed to disclose to her sexual encounters with other women, but threatened to end their deal if the relationship becomes awkward in public.

The woman, however, told the court she noticed that Mr McDonald's laptop was open by thought nothing of that fact.

After their sex, she went back to her room but discovered that her sexmate accidentally sent her a Facebook message that he had a webcam open which other male cadets could view while he was having sex with her.

She confronted him, but Mr McDonald denied there was a webcam session and the FB message was just a prank made by a friend.

The trial is expected to run for two weeks and will resume on Tuesday.