Listen to the full radio interview at NPR Morning Edition.
"JOHNSON: For experts who have followed surveillance for years, the sheer number of phone calls and e-mails the U.S. has gathered means it's almost impossible to police such a secret organization. Jennifer Granick is director of civil liberties at the Stanford Law School Center for the Internet and Society.
JENNIFER GRANICK: Mess up in a mass surveillance world, you get a massive mistake. And those mistakes have led to collection of lots of information about Americans that's supposed to be off-limits.
JOHNSON: Granick says adding new oversight, more technology and better rules might help bring those programs in line. But she's not convinced that surveillance this complicated can ever be controlled."