London (CNN) -- Rebekah Brooks, the former boss of News International, took to the stand for the first time Thursday in her trial on accusations that she was part of a conspiracy to intercept the voice mails of high-profile figures in Britain.
Brooks, who formerly edited the News of the World and The Sun newspapers, is on trial alongside six others, including Andy Coulson, a former Downing Street communications director and News of the World editor.
Early in Thursday's proceedings, the judge instructed the jury to clear Brooks on one of the five charges against her in the phone hacking trial.
The jury duly acquitted Brooks of one charge of conspiracy to commit misconduct in a public office, related to a photograph of Prince William dressed in a bikini at a costume party that was acquired by The Sun newspaper.
Brooks still faces two charges of conspiracy to pervert the course of justice, one of conspiracy to hack voice mail messages and one of conspiracy to commit misconduct in public office.
Before she took the stand, the defense reminded the jury that she is not on trial "because she was the editor of a tabloid newspaper" or for working for media baron Rupert Murdoch or for "any political views she may hold" or for "the support newspapers she edited gave to one party or another."
Rather, the defense said, her trial hinges on whether she knew about and endorsed a "practice of phone hacking at News of the World during her editorship"; whether she had encouraged a Sun reporter to pay a public official; and whether she had asked her husband, Charlie Brooks, and her personal assistant, Cheryl Carter, to "get rid of things ... to cover up the practice of phone hacking or of paying public officials."
Asked by her defense lawyer Jonathan Laidlaw whether the investigations unit she had established at the News of the World had been "set up to hack," Brooks replied, "That's just not true."
She denied that the unit had engaged in "unethical if not illegal" dark arts and said she had no knowledge of phone-hacking by private investigator Glenn Mulcaire during her editorship of the newspaper. Mulcaire and the paper's then-royal correspondent Clive Goodman were jailed after pleading guilty to phone hacking in 2007.
The court earlier heard a detailed account of Brooks' career in journalism as she rose to the top of Murdoch's UK newspaper arm, News International.
Brooks described Murdoch's advice to her younger self as being to learn on the job and not to court publicity. Murdoch "wasn't very fond of editors ... going forth on Radio 4 and spouting their opinions," she said. "I made the mistake of telling them Women's Own wanted to interview me. He didn't like that at all."
Brooks resigned as chief executive of Murdoch's News International in July 2011 amid outrage about claims of widespread hacking by staff at its News of the World newspaper. She was arrested two days later.
On Wednesday, evidence presented in court that former UK Prime Minister Tony Blair had offered his services as an "unofficial adviser" to Brooks, as well as Murdoch and his son James, made headlines.
The revelation came in an e-mail from Brooks to James Murdoch, sent on July 11, 2001, only six days before her arrest, in which she said she'd "had an hour on the phone to Tony Blair."
She paraphrased Blair's advice in five points. One was to form an "independent unit" to investigate the claims, with a report to be published at the same time as the police cleared her. She should also "accept short comings" when any trials are over, the e-mail said.
Blair also advised her to "keep strong" and "definitely (take) sleeping pills," Brooks said, as well as telling her to "tough up."
Finally, she said, Blair "is available for you, KRM (Rupert Murdoch) and me as an unofficial adviser," on a "between us" basis.
Blair's office released a statement after the court revelations that said he was "simply giving informal advice over the phone" and had made it clear to Brooks that although he knew nothing of the facts of the case, it was essential to have an independent inquiry.
"Mr. Blair said that if what he was being told by her was correct, and there had been no wrongdoing, then a finding to that effect by a credible inquiry would be far better than an internal and therefore less credible investigation," it said.
Brooks held the top job at News International, News Corp.'s British subsidiary, for two years after editing the country's best-selling daily tabloid, The Sun, and its best-selling Sunday tabloid, News of the World.
Once feted as a rising star in British media, she was the youngest person to edit a national British newspaper.
But after sweeping allegations of illegal eavesdropping by News of the World journalists when she was editor, she has seen her fortunes fade and was arrested and questioned several times by police investigating hacking before being charged.
News International is News Corp.'s British newspaper arm. The fallout forced Murdoch to shut down the News of the World in 2011.
CNN's Carol Jordan contributed to this report.