A large trove of electronic communications cited as evidence in the US Department of Justice's copyright infringement case against Kim Dotcom and his company Megaupload were "illegally" obtained, the lawyer representing the file sharing service claims.
Over the weekend, the US DoJ released a 191 page document [PDF] laying out its evidence in the case against Dotcom and his associates.
It cited a large body of captured email messages and Skype conversations between the Megaupload associates, in which they discuss copyright infringement issues and other business relating to the file storage site.
The messages were captured since 2007 and up to the 2012 special forces style raid with helicopters and armed police on Dotcom's Mega mansion in Auckland, the court documents show.
How the messages were obtained is not detailed, however.
Megaupload lawyer Ira Rothken told iTnews the interception of Skype conversations and email messages between Megaupload associates was unlawful.
"There are a number of ways the messages could've been obtained, through malware or packet sniffing, but we believe they were illegally obtained," Rothken said.
Affidavits released earlier this year show New Zealand police were using the NSA PRISM mass surveillance system to intercept Dotcom and associates' communications.
Prior to Microsoft's 2011 acquisition of Skype, messages between users of the service were thought to be very difficult to intercept. Skype used a decentralised architecture where strongly encrypted messages were passed directly between users without going through a central server.
After 2011, Microsoft collaborated with the US National Security Agency to provide the latter with access to Skype users' communications, documents leaked by Edward Snowden show.
New Zealand courts have already ruled that the raid on Dotcom's mansion and the preceding spying on his communications was unlawful.
The Megaupload founder has taken legal action against the New Zealand police and the country's main signals intelligence spy agency, the Government Communications Security Bureau (GCSB), over the spying and is seeking compensation.