This is the Cato Daily Podcast for Wednesday, August 30th, 2017.

I'm Caleb Brown.

A clear understanding of the surveillance that governments conduct without a warrant demands a clear

understanding of the protections of the Fourth Amendment.

Jim Harper is co-author of a new Cato Institute brief in the case of Carpenter v United States, which goes before the US Supreme Court soon.

We spoke earlier this month.

This case has elements of several different things that we typically see with cases involving surveillance.

We have warrantless tracking.

We have what's called the third party doctrine and they sort of

combine here to form is this is this a really good opportunity bottom line

for the court?

It's a great opportunity, and you're right, that this brings together a lot of important threads

that are out there for the court to weave together into one would hope new doctrine. The case the case is a straightforward robbery case where Timothy Carpenter and his colleagues were charged with a string of robberies.

Evidence gathered about them included data about where they had been over a period of I think 120 days or something like that.

That data was acquired from their cell phone providers, T-Mobile and Metro PCS.

For a cell phone to work, it has to connect to local cell towers.

And to improve their services, cell phone providers

keep track of what phone connected when and where. That data is kept for a good

long while for their business purposes and the government is using it in investigations

like this to figure out who's been where. The data confirmed

that they had been at the location of these various crimes they were suspected of.

Okay so this is Miranda in a way because Miranda wasn't a good guy and yet made some important case law for courts and

...