A government worker described herself as being “as drunk as she’d ever been in her life” on the night she alleges she was raped inside Australian Parliament House, a prosecutor told a jury on Tuesday.

In his opening address, prosecutor Shane Drumgold told the jury the level of Brittany Higgins’ intoxication was important because it was relevant to her ability to consent to having sex.

Fellow employee Bruce Lehrmann, 27, has pleaded not guilty to sexual intercourse without consent and faces a potential maximum sentence of 12 years in prison if convicted.

His trial began in the Australian Capital Territory Supreme Court on Tuesday in the national capital, Canberra, overseen by Chief Justice Lucy McCallum.

Mr Drumgold outlined the prosecution’s version of events and the evidence the jury will hear throughout the case, which is expected to run for up to six weeks and hear evidence from three former ministers.

He said that on Friday March 22 2019, Lehrmann and Ms Higgins, then 24, had been out drinking with colleagues at a Canberra bar, followed by a nightclub, before leaving in a taxi together in the early hours of Saturday morning.

Ms Higgins thought she was on her way home but Lehrmann said he needed to stop at Parliament House to collect some work, Mr Drumgold told the court.

Brittany Higgins (centre) arrives at the Australian Capital Territory Supreme Court in Canberra (Mick Tsikas/AAP/AP)

Lehrmann told guards via the intercom at a building entrance that he worked for Defence Industry Minister Linda Reynolds and the pair were picking up documents.

Mr Drumgold told the jury the guards who saw the pair into the building observed they were affected by alcohol.

Ms Higgins alleges that, after they both entered Ms Reynolds’ office, she fell asleep on a couch and woke up to Lehrmann having sex with her.

After Ms Higgins “said ‘no’ half a dozen times”, Lehrmann left the building in an Uber and she fell back to sleep, Mr Drumgold said.

The prosecutor said she woke up alone in the office later that morning when a guard checked on her. In text messages after the alleged rape, Mr Drumgold said Ms Higgins told a friend she had been “barely lucid” at the time.

“If he (Lehrmann) thought it was OK why would he have just left me there?” Ms Higgins asked in the message.

Defence lawyer Steven Whybrow said US writer Mark Twain’s quote “never let the truth get in the way of a good story” rings true in the case.

He said there are “massive holes” in the version of events Ms Higgins gave to police.

He said that, while violence against women is an “underreported and under-prosecuted scourge on our society”, the story Ms Higgins had told was not true.

“This verdict in no way affects the conversations and the focus that is being turned to these issues. We have all known for some time these things are real,” he said.

Before the trial began, the judge reminded jurors of the importance of impartiality.

She described the case as a “cause celebre” due to its high profile.

“It is a fundamental requirement that a person accused of a serious criminal offence be tried by an impartial jury,” she told potential jurors.

“I’m asking you to consider your own state of mind (with) the issues that will arise in this case and honestly consider if you can be impartial … and give a true verdict according to the evidence.”

A panel of 16 jurors including four reserves were selected for a trial that is expected to run for between four and six weeks. There are 10 men and six women jurors.

Ms Higgins’ allegation and complaints of a lack of support from within the former conservative government ranks provoked nationwide protests about the treatment of women in politics and prompted former prime minister Scott Morrison to offer an apology.

Ms Reynolds has been named as a witness in the trial, along with former ministers Michaelia Cash and Steven Ciobo.

The Associated Press does not usually identify alleged victims of sexual assault, but Ms Higgins has chosen to identify herself in the media.

Mr Morrison’s government lost power at May elections after nine years in office.