In short: 

The defamation trial between Senator Linda Reynolds and Brittany Higgins has heard testimony from the Senator's partner, Robert Reid.

Mr Reid told the WA Supreme Court of the sharp decline in Senator Reynolds' health after Brittany Higgins' rape allegations were covered in the media.

What's next:

The trial is due to continue until early September, with Ms Higgins expected to give evidence in the last week of August.

Liberal Senator Linda Reynolds's partner has testified her cardiologist thought she could die after she collapsed in the senate following intense pressure over her handling of Brittany Higgins' rape allegation.

Robert Reid gave evidence in the Western Australian Supreme Court on Monday during the defamation trial brought by the Senator against her former staffer Ms Higgins over a series of social media posts.

Mr Reid told the court of the significant deterioration in his partner's health after the 2019 rape allegation was made public, in an article by journalist Samantha Maiden and in Ms Higgins' interview with Channel 10's The Project on February 15, 2021.

Senator Reynolds maintains both pieces contained "false allegations" and "lies" by Ms Higgins about her handling of the alleged sexual assault, in Senator Reynolds's ministerial suite at parliament house.

In the days after the news broke, Senator Reynolds faced continuous questioning by Labor senators in question time.

Senator portrayed as 'villain'

Her lawyer Martin Bennett has told the defamation trial she was portrayed nationally as the "villain" in the story.

Mr Reid recalled receiving a message to come to parliament on March 23, 2021 after Senator Reynolds had collapsed and gone back to her ministerial suite.

He said when he saw her, "she looked white, she looked almost dishevelled, it was very painful".

On medical advice, they drove to a nearby hospital to have her heart checked, given she had a pre-existing heart condition.

"Linda was still crying," Mr Reid said.

They saw a cardiologist. 

"He said 'we might lose her'", Mr Reid said, breaking down in tears.

"He said 'this is very serious'."

The doctor though, did not admit Senator Reynolds and instead advised sending her home and monitoring her closely.

'Linda felt stupid'

Her speech to the National Press Club the next day was cancelled, and she went on leave for three weeks.

Mr Reid said watching the interview on The Project had been a major shock.

"Linda felt stupid at that point," he said.

"She had been trying to do the right thing by Brittany, not telling anyone ... and here was a plan to bring her down, and potentially to bring Scott Morrison and the government down.

Brittany Higgins claims Linda Reynolds mishandled her allegations she had been raped in the Senator's office. (AAP: Bianca De Marchi)

"It was a hit on Linda.

"She told me she could not understand why the hatred."

A central plank of Senator Reynolds' argument in the defamation trial is that Ms Higgins and her now husband David Sharaz had formulated a plan to publicly reveal her rape allegation "as a weapon to inflict immediate damage upon (Senator Reynolds) and the then government".

Her legal team claims Ms Higgins and Mr Sharaz acted with malice and caused her not only severe reputational damage, but also caused her to suffer distress and embarrassment.

Senator Reynolds wipes away tears during Question Time in February 2021. (AAP: Mike Tsikas)

Ms Higgins claims Senator Reynolds mishandled the rape allegation and failed to properly support her in the aftermath.

Bruce Lehrmann was charged with Ms Higgins's rape, but his criminal trial was abandoned due to juror misconduct and no findings were made against him. He has always maintained his innocence.

He was found to have raped Ms Higgins on the balance of probabilities in a separate civil trial. He is appealing that finding.

The trial is due to continue until early September, with Ms Higgins expected to give evidence in the last week of August.