Kate McClymont first detailed allegations against the longtime shock jock in a December 2023 article, leading to his arrest at his harbourside home nearly a year later.
The Australian Media Hall of Fame inductee told the court she had spoken to three of five complainants who allege Jones indecently assaulted or sexually touched them without consent between 2003 and 2020.
The Sydney Morning Herald's chief investigative reporter was flanked by editor Jordan Baker as she entered a Sydney court to testify against Jones on Tuesday.
She was asked about the feud between Jones and former 2GB mornings host Ray Hadley, who the court has previously been told were in a dispute over the coveted breakfast slot.
Under cross-examination by Jones's barrister Gabrielle Bashir SC, McClymont said she couldn't recall whether she knew Hadley had tried to unseat Jones from the slot in 2019.
"You understood at the time Mr Hadley had animus towards Mr Jones?" Ms Bashir asked.
"Possibly, but it wasn't something that weighed on my mind," the journalist replied.
She agreed a former radio staffer allegedly indecently assaulted by Jones told her Hadley had an "axe to grind" with Jones during their interview.
The pair met months before McClymont published her first article on Jones, which included his anonymised allegations that he had been repeatedly kissed and groped by the ex-radio host, including while driving.
McClymont said the fact he had first confided in Hadley and her stablemate and avowed "anti-Jones" journalist Peter FitzSimons did not affect the complainant's credibility.
The multiple Walkley award winner rejected Ms Bashir's suggestions it enhanced her reputation to publish special investigations under her name.
She disagreed there was a profit motive for newspaper reporting, telling the court selling newspapers was "not my problem".
McClymont told the court she didn't know what effect her Jones articles had on readership figures for the Sydney Morning Herald.
"Alan Jones is a divisive figure," Ms Bashir asked.
"If you say so," the journalist replied, prompting chuckles from onlookers.
McClymont said she always sought comment, either by text or email, from Jones before publishing her articles.
She told the court she hadn't offered any money or benefits to the three complainants whose allegations she reported on, and they had not received any benefits from her employer.
The account of a man who was allegedly kissed and groped by Jones as a 17-year-old was anonymised after his mother passed on his contact details.
He told the journalist he feared losing Jones's financial support when the septuagenarian kissed him without consent at his NSW Southern Highlands home.
McClymont's reporting prompted a famous athlete to go to police with his own claims of being indecently assaulted and sexually touched without consent by Jones years earlier.
Another complainant - an executive - reached out to the journalist about his experience with Jones after reading her article, but insisted he hadn't given her permission to write about it.
The first complainant told the court he didn't know anything about McClymont.
Jones studied her from across the courtroom as she gave evidence but the pair didn't appear to make eye contact.
Now 85, Jones has pleaded not guilty to 21 charges of indecent assault and sexual touching without consent against the five complainants.
Ms Bashir argued during her opening address that her client's media rivals were involved in at least two of the allegations against him.
"Rivalry, treachery, double dealing, money, hatred, desperation, opportunism and more are at the heart of this case," she declared in August.
McClymont is the latest of several high-profile media figures to testify in Jones's trial, including Hadley and FitzSimons.
The trial was paused at 3pm to allow Jones - an avid horse racing fan - to watch the Melbourne Cup.
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