Can they do it retrospectively though?
That depends on what data has been collected.
A lot can be done with mobile phones. And this is not a myth! If you read the info from Snowden from the Guardian newspaper, the US collects the data on everyone on this earth, all phone calls, all internet searches etc.. and the UK is one of I think 4 countries that has access to this..
For example this is from the Guardian report: When Snowden met the solicitors while in Hong Kong, although their phones were all switched off, he said they can easily be turned into a microphones even if switched off.. so he said the only way to be sure is to put the mobile phones in the fridge, so he put all of their phones in the fridge and then they started talking.
One would think the Snowden is being paranoid, but IMO the guy knows what he is doing and also the Guardian did not lie about his report.
Only what I am not sure is when this level of surveillance upon everyone has started.. I think it is mentioned it was done under George W Bush and I have no clue when G W Bush came into office.
At least, the surveillance data can be used for a good cause.
I remember back in the 2007 there was also a talk about the US satellite surveillance of the area.. i.e there was a possibility that US has recorded the movements in PDL at that night from their satellite pointing there but the answer from the US was that the satellite was turned to another angle and was not filming the area.. so maybe not, but now after all of the info from Snowden I am thinking there must be something in their data they collected which can help this case.
