Because it has been discovered that Newscorp systematically wiped its email archives of everything relating to their phone hacking activities, which pretty much had to had the assent of James, and probably Rupert, Murdoch:

Police are investigating evidence that a News International executive may have deleted millions of emails from an internal archive in an apparent attempt to obstruct Scotland Yard’s inquiry into the phone-hacking scandal.

The archive is believed to have reached back to January 2005, revealing daily contact between News of the World editors, reporters and outsiders, including private investigators. The messages are potentially highly valuable both for the police and for the numerous public figures who are suing News International (NI).

According to legal sources close to the police inquiry, a senior executive is believed to have deleted “massive quantities” of the archive on two separate occasions, leaving only a fraction to be disclosed. One of the alleged deletions is said to have been made at the end of January, just as Scotland Yard was launching Operation Weeting, its new inquiry into the affair. The allegation directly contradicts NI claims that it is co-operating fully with police in order to expose its history of illegal newsgathering.

The alleged deletion of emails will be of particular interest to the media regulator Ofcom, which said it had asked to be “kept abreast” of developments in the Met’s hacking investigation, so it can assess whether News Corp would pass the “fit and proper” test that all owners of UK television channels have to meet.

So now we have a fairly clear case of obstruction of justice and most, if not all, of the information that was deleted is still likely squirreled away in the system where it can be found with a extensive investigation.

I cannot imagine that this did not go on without the explicit approval of one of the Murdochs.