The former defence minister is suing Ms Higgins over a series of social media posts containing alleged mistruths that she believes have damaged her reputation.
Senator Reynolds said after days of scrutiny following a News Corp article and Network Ten's The Project episode about Ms Higgins' alleged rape and mistreatment, she started to break down in parliament.
Linda Reynolds said Scott Morrison was "incredibly compassionate" after she broke down. (Mick Tsikas/AAP PHOTOS)
"I was increasingly distressed. I was in incredible pain from my heart," she told the Western Australian Supreme Court on Tuesday.
"I couldn't read what was on the piece of paper ... everything was blurry ... my knees started buckling."
She left the senate chamber and was ushered into Senator Dean Smith's office.
"I just started bawling uncontrollably ... I just literally was completely and utterly incoherent," she said.
She said then-prime minister Scott Morrison consoled her after Question Time.
"He was just fantastic. He just sat with me. He just talked with me. He was incredibly compassionate," she said.
"He was sharing with me how difficult it was for him being accused of covering up a rape and the challenges, the difficulty it was causing for his girls."
Senator Reynolds, who is monitoring her heart rate while giving evidence, said she felt humiliated after her breakdown was publicised.
"I wasn't sleeping. I was quite teary. I was not in a good headspace," she said, adding she had received a "continual barrage of the foulest social media trolling."
She was admitted to hospital, where she was diagnosed with a cardiac disorder.
Labor Senator Kimberley Kitching died from a suspected heart attack in 2022. (Mick Tsikas/AAP PHOTOS)
Senator Reynolds also linked the death of Labor senator Kimberley Kitching to the Higgins saga.
She said the late Senator Kitching warned her in parliament in early-2021 that the Labor Party "knew about the incident in my office two years prior to that and that they were going to rain hell on me and the government".
Senator Reynolds said she was "incredulous" Labor would make such a plan and that she elevated the issue to the prime minister's office, before telling the court her blood pressure was rising.
Justice Paul Tottle suggested adjourning the court, to which Senator Reynolds replied: "Thank you, this is a particularly emotional point, given that it led to Senator Kitching's death".
Senator Kitching died from a suspected heart attack in 2022.
Senator Reynolds said the media stories about Ms Higgins' allegations initially made her "incredibly angry".
"I was incredibly hurt and (Ms Higgins) could not have picked a worse issue to bring me down," she said as her lawyer Martin Bennett read through Samantha Maiden's article.
Linda Reynolds said Brittany Higgins could not have picked a worse issue to bring her down. (Richard Wainwright/AAP PHOTOS)
"It is such an abhorrent, horrid thing to say to any woman, that you've mistreated their rape allegation and not only that, you've covered it up.
"I was angry at Brittany but I was also angry at myself and just wondering how we had got it so wrong."
Senator Reynolds said she was left confused about what cues she had missed.
"I genuinely felt sorry for her ... how could, two years later, our recollections be so different of what we did and what happened at that time?" she said.
She said she felt sick watching The Project episode and, out of frustration and anger, described Ms Higgins at the time as a "lying cow".
"Certainly it characterised how I was feeling," she said, recalling for the court how she was later forced to apologise for the comment.
Ms Higgins' defence relies on truth and that it was reasonable to comment and provide opinion on issues of public interest concerning government and political matters.
She alleged that colleague Bruce Lehrmann raped her in Senator Reynolds' office in 2019.
Lehrmann has always denied the allegation and his criminal trial was derailed by juror misconduct.
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