Carpenter v. United States

[W]hen the Government tracks the location of a cell phone it achieves near perfect surveillance, as if it had attached an ankle monitor to the phone’s user.

The Court, in Carpenter v. United States, relying on the above premise, recently held that “[t]he Government’s acquisition of the cell-site records was a search within the meaning of the Fourth Amendment.”

Here the progress of science has afforded law enforcement a powerful new tool to carry out its important responsibilities. At the same time, this tool risks Government encroachment of the sort the Framers, “after consulting the lessons of history,” drafted the Fourth Amendment to prevent.

Cell phones and the Fourth Amendment. Which doctrine controls? Jones, Katz, Smith? No one really knows…