The white cocktail dress stayed there, "like this weird anchor", until she decided she could not do both and "very symbolically" washed it, the former Liberal Party staffer told a jury on Thursday.

Ms Higgins spoke from the witness stand in the ACT Supreme Court, where she is continuing to give evidence on the third day of former colleague Bruce Lehrmann's rape trial.

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Lehrmann has pleaded not guilty to a charge of engaging in sexual intercourse without consent.

He denies any form of sexual activity occurred with Ms Higgins in the ministerial office of their boss at the time, Senator Linda Reynolds, at Parliament House early on a Saturday morning in March 2019.

It is the prosecution case that he raped her on a couch in the office after "a drunken night out".

Thursday's evidence began with Ms Higgins choking back tears while watching Parliament House CCTV footage, captured on the morning of her alleged rape, for only the second time.

The video showed Ms Higgins and Lehrmann passing through metal detectors moments after the latter, wearing a blue collared shirt, told security staff they had been "requested to pick up some documents" and he had forgotten his pass.

"I don't remember any of this," Ms Higgins said, describing her level of intoxication at the time as "very high".

Ms Higgins was subsequently seen running after Lehrmann and a security guard to catch up as the latter escorted them to the office of Senator Reynolds, then left them alone after they went inside.

The jury was then shown photographs from inside the ministerial office, including the couch on which Ms Higgins claims to have been raped, as she described her positioning at the time of the alleged attack.

Eventually, the security video showed the pair leaving Parliament House several hours apart.

Prosecutor Shane Drumgold SC subsequently showed the jury a picture Ms Higgins took of her thigh, on which there was a visible bruise, which she said she assumed had come from the alleged rape about five days before the image was captured.

A photograph of the dress, which was given to police about two years after the alleged incident, was also displayed on screens within the courtroom as Ms Higgins explained what she had done with it.

"I kept it under my bed, in a plastic bag, for a good six months, untouched, uncleaned," she said.

"I just had it there ... It was like this weird anchor for me."

After eventually deciding to wash it, Ms Higgins said she wore it once more before giving it to police when she resolved to leave behind her Liberal Party work and pursue a formal complaint last year.

Text messages between Ms Higgins and a former boyfriend, Ben Dillaway, were also discussed in court on Thursday morning.

The relevant messages began three days after the alleged rape, when Ms Higgins wrote: "So, I think I might not continue to be employed with Linda."

She added that something "pretty bad" had happened and she did not know how it was going to play out, or even how she wanted it to play out.

Eventually, she disclosed that she did not remember how she had ended up at Parliament House in the early hours of the morning in question.

"[V]aguely remember Bruce being there and then I woke up in the morning half dressed by myself in the Ministers office on Saturday morning," Ms Higgins wrote.

Later in the conversation, she told Mr Dillaway: "I was barely lucid. I really don't feel like it was consensual at all. I just think if he thought it was okay, why would he just leave me there like that."

The trial continues.