This is the Cato Daily Podcast for Tuesday, August 30th, 2016.

I'm Caleb Brown.

Police in Baltimore have been engaging in surreptitious mass-scale camera

surveillance with apparently no authorization whatsoever.

Jim Harper, a senior fellow at the Cato Institute, argues that kind of surveillance is effectively pre-search.

Setting the table for the use of future general warrants by police.

We recently learned that in Baltimore, they've been using mass-scale camera surveillance by flying a specially equipped plane that would cover something

like 30 square miles for as much as 10 hours at a time with gathering footage.

The footage could be reviewed at any time after its collection so that if an event were

to happen, you could say,

let's go see what happened at that corner

and then see what happened before and afterwards as well.

So before an incident happens and before police arrive at an incident, you have at least a glimpse of what happened.

So you can track the movements of cars, track the movements of people, though they represent only a, say, a pixel in the image that's

collected, but you can see where that pixel goes.

And if it goes to a particular address, you can figure out who lives there and use that information

to triangulate on suspects.

So a valuable law enforcement tool,

but equally a tool that could threaten and invade privacy.

It could invade privacy any number of ways, but it would allow observation

or reconstruction of who had attended a protest.

If there's someone who's an opponent of the police department,

...