A former University of Canberra law professor has faced questioning in court about why he showed a pornographic image to a student during a meeting about alleged plagiarism.

Arthur Marshall Hoyle, 67, is on trial over alleged sexual offences against five students.

One of the students alleged she was raped by Hoyle in his office, during a discussion about the alleged plagiarism.

Another said he showed her pornography, including child pornography, in a power point presentation he had compiled about websites that had been revealed, when her assignment was scanned for word matching.

Hoyle denied there was any child pornography.

But he admitted he had included three pornography sites in the presentation, which he said were listed by the software used to scan the work for plagiarism, including an image from one site that was blown up to obscure the details.

Prosecutor Trent Hickey questioned what Hoyle thought he was doing.

"How on Earth can a person plagiarise from a pornographic website?" he said.

Mr Hickey asked why he had focused on the site: "Why were you so worried about the porn site?"

Hoyle replied: "I've asked myself that since."

Hoyle said he wanted to give the student the full picture of what had emerged and also what he was preparing to show others higher in the administration.

"It was definitely a bad judgement on my part," he said.

I was extremely distressed: accused

Mr Hickey also pressed Hoyle on the circumstances of the meeting, suggesting he had seen an opportunity to take advantage of a student in a vulnerable position and had used the power point presentation to add to that.

Hoyle denied that saying: "I did not show her a pornography site."

He said the woman had become very upset, which had in turn upset him.

"I was extremely distressed by this," he said.

"I deny totally I did anything improper."

Hoyle has denied all 10 charges.

The trial will continue next week.