British broadcaster Sky News says executives authorised the hacking of emails on two separate occasions, claiming it was in the "public interest".
The online and television news service, part-owned by Rupert Murdoch's News Corporation, said in a statement that does "not take such decisions lightly or frequently".
It comes after months of government inquiries into phone and email hacking, with two separate police investigations looking into police corruption and claims made by public figures.
The broadcaster revealed it hacked into the email account of John Darwin, the "canoe man" who faked his own death more than a decade ago, and was subsequently jailed for deception in 2008 along with his wife, Anne.
The reporter, Gerard Tubb, Sky News' northern England correspondent, built up a database of emails that he believed could have proven the prosecution's case when Darwin's wife stood trial, according to The Guardian. She had pleaded not guilty, while her husband pleaded guilty to six counts of fraud and deception. The two were jailed but released in 2011.
Sky News said that after accessing the emails, it handed the evidence it collected to the police, which was "pivotal" to the court case. Cleveland Police said in a statement that it had "conducted an initial review into these matters and can confirm that enquiries are ongoing into how the emails were obtained."
The same reporter also accessed the email accounts of a suspected child sex offender and his wife, but did not lead to any details being published, according to a statement released by the broadcaster.
Sky News' managing editor Simon Cole approved the hacking. John Ryley, the head of Sky News, said the decision required "finely balanced judgement", and stood by the reporter.
Sky News' parent company, British Sky Broadcasting (BSkyB) is being investigated by UK communications regulator Ofcom. The independent inquiry could find BSkyB being found not a "fit and proper person" to hold a broadcasting licence, which could have drastic effects on the company.
News organisations can break the law in some instances for reasons to serve the public interest. Sky News cited an example of a journalist buying an Uzi submachine gun in the UK, a weapon outlawed by gun-control laws. In some cases, broadcasters and news organisations can break secrecy laws if their home governments are themselves in breach of the law.
But the controls and delicate balance of reporting can often find the news agencies in trouble.
Intercepting email is illegal under the UK's Computer Misuse Act, which can send people to prison for 10 years for serious breaches. Since the start of the phone hacking scandal, an independent inquiry was set up, a Murdoch-owned newspaper was shut down, and many current and former News Corp. journalists and editors, including its chief executive Rebekeh Brooks, were arrested.
A Sky News spokesperson was unavailable for comment beyond the statement given.