Is reading a license plate on a public road an invasion of privacy, though?
Looking inside your car might be, but anyone can read a license plate.
Looking inside your car might be, but anyone can read a license plate.
For one example take the paparrazi. While many people consider what the paparrazi does to be an invasion of privacy, it is not legally defined as such, and is therefore legal. Now imagine if there was a paparrazi on every single street corner, wirelessly connected so that any time any person of interest passes through any intersection, a photo of them with a timestamp is uploaded to the internet instantaneously. Would that be an invasion of privacy? Now what if these same paparrazos on every street corner just so happened to not be real people, but cameras covering every angle of the intersection? How quickly what "isn't an invasion of privacy because you're in public" becomes a terrifying scenario.
The words "reasonable expectation" come to mind, and in my mind, it's not "reasonable" to expect that anything you do in public remains private just because someone never bothered to connect the dots.
That seems a mighty arbitrary line to draw in the sand, in other words. We already have laws against stalking and the like - how about we enforce those instead of creation of new, conflicting laws?
There's also the problem of any laws conceived to address this problem have free speech concerns.
I'm not saying I agree with the whole "mosaic" definition of things, but I think the point is worth pondering: Sometimes the information itself isn't the point of contention, it's how the information is aggregated.
First, its an objective test, which means reasonableness is based on factors such as democratic accountability, personal autonomy, threats of government abuse, etc.
Second, it's only "reasonable" at an individual level to expet your public locations are being logged if you expect the police have the resources to put a tail on every person in America, which is crazy (Kevin Bankston and Ashkan Soltani have a great paper on "costs" of surveillance and location tracking specifically: http://www.yalelawjournal.org/forum/tiny-constables-and-the-...). The aggregate effect of monitoring everyone's location is a very new concept, and appears very unreasonable based on social norms.
As far as arbitrariness of drawing lines, I think a clear distinction can be made in use of electronic devices to generate location data (in establishing a legal standard the question gets more complex; I recommend looking at writings on topic by Prof. Susan Freiwald, who has done excellent research on the issue). Basing a rule on use of electronic devices is the path states are going down to address both demands for cell phone location data, and directly obtaining location data through devices such as stingrays. It's a simple approach with a clear line that directly gets to the problem of electronic generation of data giving the government unprecedented power regarding location data.
quantitative change leads to qualitative change at some point.
What happens if I make the same 20 turns as you, though, at the same intersections, right behind you? At first it was a coincidence, but after a certain number of turns, it's probably not.
What if I did this every day for a year? You could probably get a restraining order against me for stalking. But for two turns one day last year? Definitely not.
The outward behavior is exactly the same, I just happened to be following behind you (that's what I'll argue). Why should the courts treat a couple of blocks any differently than many miles for many days?