The former editor of the 'Sun' and erstwhile 'News of the World' tabloids is on trial over allegations of phone hacking as well as conspiracy to commit misconduct in a public office by authorising payments to public officials including police officers.
During her cross-examination at the Old Bailey court in London, she stressed that she had never knowingly paid a public official for a story.
"I don't think every cash payment was seen as illegal or evidence of criminality, they had always been there," she said.
When asked by Prosecutor Andrew Edis QC if she cared how her journalists were dealing with public officials, Brooks said "it was a constant dialogue".
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On her 12th day in the witness box, Brooks said the 'Sun' may have paid officers for information, such as gossip about a neighbour, that he or she may have picked up off duty.
She was also repeatedly asked by Edis if she had thought about whether a military source paid for supplying stories to the 'Sun' was a public official.
The court heard that in 2006 she received a request from a reporter for authorisation to pay 4,500 pounds to a source whose name and details she did not know.
Edis asked: "Did you think at all about whether it was a public official?" Brooks replied: "My assumption was it was not a public official."
Brooks and seven other defendants deny all the charges against them.
Brooks has already been acquitted on a fifth charge in relation to the picture of Prince William at a fancy dress party after the jury was directed to find her not guilty of the charge by the judge.