Mistrial in case of Bruce Lehrmann, charged with raping Brittany Higgins at Parliament House

A sheriff's officer inadvertently made the discovery during "routine cleaning" on Wednesday afternoon, when he accidentally knocked over one of the jurors' folders and saw the document's title.

Chief Justice Lucy McCallum said the research paper was about sexual assault, and in particular the reasons behind false complaints and scepticism in the face of true complaints.

After questioning the juror responsible in closed court on Thursday morning, the judge discharged them.

She then discharged the balance of the jury in open court, telling the rest of its members she "regrettably" had to discharge them as well as a result of the "mishap".

"Material has entered the jury room that ought not to have," the trial judge said.

Chief Justice McCallum later said while the juror behind the misconduct claimed the jury had not relied upon the paper in any way, it was "beyond question" that the trial had to be aborted.

The judge said she had warned jurors at least 17 times not to undertake their own research.

"It goes without saying that this is both an unexpected and an unfortunate outcome in this trial," she said.

The judge then granted Lehrmann bail, with conditions including that he must appear for a retrial on February 20, 2023, if the Director of Public Prosecutions chooses to run the case again.

The discharging of the jury came more than three weeks after defence barrister Steven Whybrow opened Lehrmann's trial with the assertion the public had been "sold a pup" with the story of the 27-year-old having allegedly raped Ms Higgins.

Lehrmann, who pleaded not guilty to a charge of engaging in sexual intercourse without consent, denied any sexual activity with Ms Higgins in the early hours of March 23, 2019.

It was on that morning, following what prosecutor Shane Drumgold SC called "a drunken night out", that Lehrmann and Ms Higgins attended Parliament House about 1.40am.

The pair, minus their staff passes, were escorted to the suite of the then-defence industry minister, Liberal senator Linda Reynolds, for whom they both worked at the time.

Lehrmann left about 45 minutes later without Ms Higgins, who was later spotted, naked and passed out, on a couch when a security guard went to check the minister's office.

While Lehrmann insisted he never even entered that particular room, claiming he had instead being working elsewhere in the suite, Ms Higgins told the court she had woken up on the lounge as he sexually assaulted her, leaving her feeling "trapped" and "not human".

Ms Higgins publicly revealed the alleged rape in media interviews nearly two years later, kickstarting what Chief Justice McCallum described as "a cause celebre".

Though jurors were told of how the alleged victim had appeared on television and spoken at public events, they were repeatedly told to only take into account the evidence they heard in court and to ignore the work of the reporters "practically hanging from the rafters".

They were asked to scrutinise key issues that included why Lehrmann had gone to Parliament House with Ms Higgins in the early hours of a Saturday morning, and whether he had lied about the reason.

The jury heard the alleged rapist had variously explained his trip by saying he went to pick up documents, to collect his keys, to work on "question time" stuff, and to drink whisky.

The inconsistency in what he told Parliament House security and Senator Reynolds' chief of staff was, the court heard, partly why he was subsequently sacked by the politician.

But it was Ms Higgins' credibility at the heart of the case, with Mr Drumgold describing her as a reliable witness who had told all manner of people a consistent story of being raped.

The prosecutor tried to persuade the jury Ms Higgins had been "right to be scared" of pursuing a police complaint against Lehrmann, claiming "strong political forces" were at play as she faced the choice of reporting the accused or keeping her "dream job".

The 2019 federal election was looming when Ms Higgins initially decided against taking police action, only to change her mind in early 2021 after cutting her Liberal Party ties.

However, Mr Whybrow suggested claims of political pressure being applied to keep Ms Higgins quiet were "a paper tiger".

The defence barrister suggested Ms Higgins had delayed making a police complaint because she had fabricated the rape claim by "piecing together" patchy memories from a night she really could not recall.

He claimed she first concocted the story days after the alleged incident, while worried she would lose her job as a consequence of Parliament House security having seen her, in a state of undress, in a senator's office in the middle of the night.

As for why Ms Higgins had continued to press the allegation after it turned out she would not be sacked, and after having ultimately resigned of her own volition nearly two years later, Mr Whybrow suggested she had at least 325,000 reasons for doing so.

This was a reference to a $325,000 book deal secured for Ms Higgins in March 2021, the month after she went public with her claims in interviews with The Project and news.com.au.

While Lisa Wilkinson and Samantha Maiden, the high-profile journalists responsible for the initial revelations of Ms Higgins' allegations, were ultimately cut from a lengthy prosecution witness list, some political heavy-hitters were required to give evidence.

They included Senator Reynolds and Ms Higgins' subsequent employer, fellow Liberal senator Michaelia Cash, who both rejected the suggestion the public airing of allegations one staffer had raped another would be "politically embarrassing" for the party.

On one of the most dramatic days of the trial, Mr Drumgold accused Senator Reynolds of attempting to "coach" Mr Whybrow's cross-examination of Ms Higgins.

Senator Reynolds denied the claim and insisted she had not known it was inappropriate to send Mr Whybrow "tips" about certain text messages while he was questioning Ms Higgins.

The senators were among the last of 29 witnesses to testify in a trial that largely vanished from public view for a week because of a temporary non-publication order imposed in relation to all evidence given while Ms Higgins was, midway through cross-examination, absent from the witness stand.

Her return and the completion of her evidence once again kick-started what Mr Whybrow described in his opening address as "an unstoppable snowball" of media coverage.

But for all the opinions expressed about a case that captured the attention of the nation, the only views mattered in the eyes of the law were those of the eight women and four men on the jury tasked with deciding what Mr Whybrow dubbed the $325,000 question.

Did Bruce Lehrmann rape Brittany Higgins at Parliament House on March 23, 2019?

Nearly two years after the case first came to the public's attention, that question remains unanswered.

More to come.

MORE COVERAGE OF THE TRIAL: