First of all, the NSA have a copy of your entire hard drive or whatever storage you have, without your consent, as an image file! got it?  Your computer knows all … and tells all!  BUT WAIT! nope! not just your computer but all your mobile devices as well including cell phone, pda, tablet, ipad you name it! yeah sure delete and trash and empty all cookies you want! even I can recover what you’ve deleted   , let alone the police! so be careful what you search, what you watch, what you wrote http://www.cnn.com/2014/07/02/tech/web/digital-evidence/index.html?hpt=hp_c2