Sky News has said it illegally hacked emails belonging to members of the public on two separate occasions.
The broadcaster said it hacked emails from John Darwin, who faked his own death in a canoe, and his wife Anne.
A spokesman for Sky News said police "absolutely knew" the emails - which it passed to officers working on the Darwin case - were obtained by hacking.
Sky News said the action was in the public interest and amounted to "responsible journalism".
The second email hacking incident Sky disclosed targeted the accounts of a suspected paedophile and his wife.
The broadcaster released a statement which said: "Sky News is committed to the highest editorial standards.
"Like other news organisations, we are acutely aware of the tensions that can arise between the law and responsible investigative journalism.
"We stand by these actions as editorially justified and in the public interest."
The statement went on: "We do not take such decisions lightly or frequently.
"They require finely balanced judgement based on individual circumstances and must always be subjected to the proper editorial controls."
John Darwin was reported missing in a canoe in the North Sea in March 2002.
His wife Anne collected more than £500,000 in life insurance payouts while he hid in their marital home, allowing their two sons to think he was dead.
The pair were found guilty of the deception in 2008.
In the run-up to the trial former Sky News managing editor Simon Cole agreed North of England correspondent Gerard Tubb could hack into Darwins' Yahoo! email account.
A Sky source now has told the BBC that Mr Cole will be leaving the company in the coming weeks.
On his Twitter feed , Mr Cole later wrote: "I've been planning for some time to retire from Sky News after 17 years. This is unrelated to the Darwin story. There is no linkage. Fact."
Mr Tubb uncovered messages which cast doubt on Mrs Darwin's claim during her criminal trial that her "domineering" husband forced her to go through with the fraud plan.
Sky News said it supplied material it had gathered to Cleveland police which was "pivotal" to the court case.
A Cleveland Police spokeswoman said: "Cleveland Police has conducted an initial review into these matters and can confirm that enquiries are ongoing into how the emails were obtained."
The Crown Prosecution Service said police inquiries were ongoing. "This remains an investigative matter... but, as with any case, we will provide advice to the police if required," a spokesperson said.
It is illegal to hack into emails under the Computer Misuse Act.
Tom Watson MP, a vocal critic of Rupert Murdoch journalists during the phone hacking scandal, said of the latest development: "There are many questions that need answering.
"The chair of BSkyB needs to say something on this and reassure viewers this has not been going on more widely."
He continued: "There are cases where the public is best served with journalists breaking the law.
"But it has to be done in extremis and I am not sure whether it was in these two cases. It is too early to know."
But Peter Preston, a former editor of The Guardian newspaper, said: "I think it's pretty clear there are [public interest defences for hacking the Darwins' emails].
"I don't see this as a story in the News of the World type at all.
"Nobody is saying there was not some real crookery here that the police weren't properly informed of."
He added: "It is when you get into the more seedy areas of stories, which don't have any public merit at all, the difficulties start."
Sky News is part of BSkyB, which is 39% owned by Rupert Murdoch's News Corporation.
BBC Home Affairs Correspondent Matt Prodger said: "It's extremely sensitive, because Sky News is a subsidiary of BSkyB, which is currently under investigation by Ofcom to see whether it is fit and proper to continue holding a broadcasting licence.
"So it is a real blow to yet another part of the Murdoch empire."