I'll quote the slip up of Tim Clemente, a former FBI agent:
> All digital communications are uh uh... There's a way to look at digital communications in the past. And I can't go into detail of how that's done or what's done but I can tell you that no digital communication is secure.
And even if they are not storing the audio recordings, wouldn't it be reasonable to expect that automatic transcription is run against the audio for search indexing and long-term storage purposes? Text transcriptions like that, even if they are imperfect, can preserve conversations with minimal storage requirements almost indefinitely.
* http://www.pbs.org/newshour/bb/government_programs-july-dec1...
* http://www.theguardian.com/commentisfree/2013/may/04/telepho...
I'll quote the slip up of Tim Clemente, a former FBI agent:
> All digital communications are uh uh... There's a way to look at digital communications in the past. And I can't go into detail of how that's done or what's done but I can tell you that no digital communication is secure.