The Bruce Lehrmann rape trial in Canberra has been ruled a mistrial after the jury was discharged.

He has pleaded not guilty to sexual intercourse without her consent.

The trial had been waiting for a verdict since late last week.

The court heard the prohibited research was uncovered when one of the court officers accidentally bumped one of the juror’s folders onto the floor.

When the officer picked up the clear plastic folder, he noticed part of a title of an academic research paper into sexual assault sticking out.

On Thursday, Chief Justice Lucy McCallum with “regret” ruled a mistrial.

“It has come to my attention that one of you.. has undertaken research in relation to issues in the case and that material has entered the jury room that ought not to have.”

“I have heard an explanation, and it may be that no harm has been done, but that is not a risk I can take,” she told the jury.

“During the course of the trial … I must have given the jury at least 17 warnings and prohibitions on undertaking any research of their own.

“This is an unexpected and unfortunate outcome in this trial,” she said.

Ms McCallum said given the circumstances, she had to discharge that juror and then the entire jury.

Ms Higgins and her partner David Sharaz were in the courtroom for the ruling.