This is an interesting and important technical discussion of how PRISM could work (and enable NSA to read, e.g., your e-mail messages) without the knowledge or consent of ISPs such as Google and Microsoft:
PRISM: Here's how the NSA wiretapped the Internet ZDNet (June 8 [sic], 2013).
N.B. ZDNet astutely noticed that President Obama parsed his words very carefully on June 7 when denying that NSA's surveillance programs are unduly intrusive.
Evidence marshaling software MarshalPlan