In what will be regarded as a benchmark decision, a high court judge set out the first prison sentence in the raft of cases arising from the phone hacking scandal at the News of the World, once the biggest circulation English language newspaper in the world, and the jewel in the crown of Rupert Murdoch’s UK subsidiary, News International, which dominates Britain’s newspaper market.

A high-ranking counterterrorism officer, Detective Chief Inspector April Casburn, was sentenced to 15 months in prison on Friday after her conviction last month for misconduct in public office for contacting the now-shuttered Sunday tabloid in September 2010, to inform them that the Metropolitan Police were reopening an investigation into phone hacking, which had previously been attributed to a “rogue reporter.”

Within months the new investigation would become a major police inquiry, Operation Weeting, which would lead to the discovery of hundreds of new phone hacking victims, including the murdered teenager Milly Dowler, and the arrests of many more journalists and senior News International management. Former CEO Rebekah Brooks, and the former News of the World editor and Government chief press officer, Andy Coulson--both good friends of the prime minister David Cameron--face trial for phone hacking-related charges in September.

In his written judgement, Judge Adrian Fulford dismissed the claims of Casburn’s lawyer, Patrick Gibbs QC, that the former officer was acting out of the highest motives because she feared important resources would be diverted from counterterrorism to phone hacking. Though no article appeared and no money was ever paid, Fulford judged the tip-off was “a corrupt attempt to make money out of sensitive and potentially very damaging information.”

“She posed a really significant threat to the integrity of this important police investigation,” Fulford wrote.

The prosecution case against Casburn relied heavily on a memo taken by the reporter on duty at the time, Tim Wood, which detailed the contents of the call and the request for payment. Wood, who was key prosecution witness, has since published an article on the Exaro website explaining how he was forced to give evidence because News International had handed over the memo, in what he calls a “betrayal” of the fundamental principle of journalism. Casburn was “sacrificed by big business, intent on protecting its reputation” Woods wrote, adding that News Corp.’s Management and Standards Committee has “gone too far, betraying more confidential sources than any other body or person in the history of journalism."

The MSC, first set up in response to the phone hacking allegations, has access to over 300 million emails from News International over the last decade, has been the major source of information on illegal payments to public officials leading to the arrests of 20 senior journalists from sister paper to the News of the World, the best-selling daily tabloid The Sun. Answering to an independent chairman in the UK, and supervised by former assistant attorney general Viet Dinh in New York, the MSC was set up partly in response to the phone hacking scandal, but also under intense pressure from the FBI, SEC and Department of Justice who launched an investigation of News Corp. under the Foreign Corrupt Practices Act in 2011. FCPA legislation makes U.S.-based corporations liable for any corrupt payments made by subsidiaries overseas. Co-operation with the authorities is the prime way a corporation under investigation can reduce possible future fines or indictments of senior personnel. One of the senior executives running the London end of the MSC , Will Lewis, was promoted on Friday to ++Chief Creative Officer at News Corp .

Also on Friday, police officers from Operation Elveden--the Scotland Yard investigation focused on corrupt payments to officials by journalists--made their 59th arrest. A 33 year old male officer in the Specialist Crime and Operations unit was arrested in North London.

Meanwhile, both journalists and police have mixed feelings about the harshness of DCI Casburn’s sentence. The judge made it clear that had the defendant not been the mother of a recently adopted “vulnerable child,” Casburn’s sentence would have been more than doubled to three years. The sentence—on the higher end of expectations--will surely send a chill through many of those awaiting charges for related offences, who were previously hoping for suspended sentences.

A former senior police officer familiar with the case told The Daily Beast “a suspended sentence would have been appropriate, bearing in mind her age and personal circumstances.” However, sources suggest Casburn will have VIP treatment in Holloway women’s prison for the first seven days, before immediate transfer to an open prison. With early release and a home detention curfew, she could be out in three months.

Meanwhile, the shadow of potential trials and charges still hang over dozens of journalists. Operation Weeting is now entering its third year, with some journalists recently having their bail until June, before they will know whether they are charged or not. This delay could reflect the complexity of the dozens of cases involved, but it could also be part of a strategy, questioning all potential witnesses before moving up the corporate ladder to lay charges against more senior management.