Not really apropos to the discussion, but, no, the biggest exception to warrant requirements isn't "plain view"; it's search incident to arrest. If you're placed under arrest for any reason, you can be searched, your person can be searched, any belongings you're holding can be searched, and your immediate vicinity (ie, the passenger compartment of your car) can be searched.
But we're not talking about search. We're talking about using technology to capture information in plain view that is explicitly made available to law enforcement.
The differences between GPS transponders and lie detector tests are numerous, including how invasive they are (having devices hooked up to your actual body), the fact that they require detaining you, and the fact that the police have absolutely no business attempting to ascertain your private thoughts, but are explicitly entitled to track your car.
(Lie detector tests are also a psychological ploy; they don't actually do anything.)
You're right and this is the key to the whole problem. The Supreme Court has ruled that the Fourth Amendment does not protect a person against a search unless the search violates a person's "reasonable expectation of privacy."
So the police can search through your garbage, phone records, or bank statements because supposedly you don't have a reasonable expectation of privacy in those things since you've abandoned/given away your garbage to the trash co, let the phone co know who you want to talk to, and allowed the bank to keep track of your money.
So, the reasoning goes, a search of those things is outside of the Fourth Amendment: it's not even a (4th Amendment) search. Even though every non-lawyer normal person knows that it is. A search is just an attempt to look for something. And people normally do expect privacy in their their garbage, phone records, and bank accounts.
So now government can use dragnet software to continually track everyone's phone calls, bank transactions, internet usage, maybe email (people allow Google to read their mail so that Google can serve up relevant ads), maybe unencrypted wifi communications. No doubt in the future government robots will comb through everyone's garbage at the dump looking for evidence of crime. Next to this, planting tracking transponders on a car doesn't seem like such a big deal.
> If you're placed under arrest for any reason, you can be searched, your person can be searched, any belongings you're holding can be searched, and your immediate vicinity (ie, the passenger compartment of your car) can be searched.
I don't think the search incident to arrest is quite that broad. The police can search you and your immediate area for weapons and evidence that may be lost or destroyed, but, for example, I don't think they could search inside a locked briefcase, sealed letter, laptop, or cell phone (see http://www.policechiefmagazine.org/magazine/index.cfm?fuseac...). They also can't search your car for evidence of a crime for which they don't have probable cause if they already have you in handcuffs in their patrol car. (http://en.wikipedia.org/wiki/Arizona_v._Gant)
> (Lie detector tests are also a psychological ploy; they don't actually do anything.)
Successful passage of a lie detector test has been enough to get prosecutors to drop rape charges in a he-said-she-said case. (I was interning at the public defender's office at the time.)
Thanks for the reply. This discussion helped me to clarify my own thinking.
But we're not talking about search. We're talking about using technology to capture information in plain view that is explicitly made available to law enforcement.
The differences between GPS transponders and lie detector tests are numerous, including how invasive they are (having devices hooked up to your actual body), the fact that they require detaining you, and the fact that the police have absolutely no business attempting to ascertain your private thoughts, but are explicitly entitled to track your car.
(Lie detector tests are also a psychological ploy; they don't actually do anything.)