Built on Facts

GPS Tracking

MarkCC on Good Math, Bad Math has been posting lately on encryption and privacy. As usual, technology has increased the number of ways the government can read your mail, but it has also increased the ways you can hide your communications as well. Modern open-source encryption is very secure and all other things being equal it’s much harder for the government to read encrypted email than it is for the government to open an envelope old-style. To read encrypted email, realistically the government is going to have to surreptitiously bug your computer and get your password, which (for the moment) requires a warrant and can be defended against to an extent. On balance technology has been beneficial to privacy in this case so long as you pay attention.

Some privacy-destructive technology is harder to counteract. Via Instapundit comes a Washington Post story about the police using GPS to track suspect vehicles. This is a great use of technology, and has caught many particularly nasty criminals. Great, that is, when the police have a warrant. Unfortunately many departments do such tracking without a warrant. What’s worse is that many courts have approved. What’s even worse is that the legislatures of the various states have not taken any action – since of course the courts are in theory only one line of defense. Your elected representatives are supposed to be another. From the article:

Across the country, police are using GPS devices to snare thieves, drug dealers, sexual predators and killers, often without a warrant or court order. Privacy advocates said tracking suspects electronically constitutes illegal search and seizure, violating Fourth Amendment rights of protection against unreasonable searches and seizures, and is another step toward George Orwell’s Big Brother society. Law enforcement officials, when they discuss the issue at all, said GPS is essentially the same as having an officer trail someone, just cheaper and more accurate. Most of the time, as was done in the Foltz case, judges have sided with police.

I’ve always loathed this “Some say X, but others say Y” style of reporting. Very often X and Y are both true. “Some say eating your neighbor’s cat is healthy and inexpensive, but others say it’s cruel and theft.” Both sides are true, but obviously one point carries a lot more weight than the other. Truth is a necessary but not sufficient condition for a good public policy. And to put it gently, the idea that GPS tracking is just like being followed by a human is… massaging the truth.

Glenn Reynolds of Instapundit had a pretty trenchant comment:

Question: If sticking a device on someone’s car — which is a trespass to chattels in tort — is okay without a warrant, then is it okay if I stick a device on a police car so I can track where the cops are going, and index it against a list of known donut shops? Or would they find something to charge me with? And if the latter, then why doesn’t the creativity go both ways?

Quite so. If something would be otherwise illegal, the police ought to have a warrant. Period.

With encryption and internet privacy, we pro-freedom types have a two-pronged attack. We can advocate public policy that’s respectful of privacy and the bill of rights, and we can also use encryption and good security practices to eliminate or minimize the effects of government intrusion.

That’s more difficult here. We can advocate stronger controls on GPS tracking, but until then there’s not any good way to prevent being tracked. I can think of two ways, but neither are very good. You could build a GPS jammer, but aside from the difficulty to everyone but electrical engineers, deliberately jamming legitimate radio signals of any kind is generally illegal. You could also built a device which detects the tracking device’s transmission, but that would be very difficult since you don’t know the frequency on which the device transmits. If indeed it transmits at all, since it could just passively record data until the police retrieve it. Maybe someone else will have a more clever idea.

Keep this in mind when voting for state representatives and local judges. Privacy is not always a big issue in the electorate as a whole, but believe it or not there are people out there who care about it. If the Founders though appropriate law enforcement search and seizeure rules were important enough to devote several amendments to, we should certainly treat it as an issue of profound importance.

Update: An Instalanche? Welcome! You’re likely in a decided political minority on ScienceBlogs, but there are a few token evil regressive reactionaries. By the prevailing standards here, I’m one of ’em. But it’s ok. They tell me dissent is the highest form of patriotism.


  1. #1 mountainguy
    August 13, 2008

    Just wondering, do you know where the police put the GPS? Underneath the car? Or inside the car under a seat or dashboard?

    If the GPS is put inside the car, that feels clearly wrong without a warrant.

  2. #2 travc
    August 13, 2008

    Easy way to find out if tracking a police car is illegal or not… ask the police. If they fail to give a clear answer, just do it (and defend yourself with their answer.) If they say it is illegal, use their rational to challenge their claimed right to do it without a warrant.

  3. #3 Paul Murray
    August 13, 2008

    “To read encrypted email, realistically the government is going to have to surreptitiously bug your computer”

    It’s rather like the “you don’t have to be faster than the lion, just faster than the slowest zebra” situation. Encryption cannot be perfectly secure. It doesn’t matter. It only needs to be secure enough that it’s more bother than it’s worth to try decrypting. Of course, how much bother it’s worth depends on what you’re encrypting, so there’s always a niche for every level of security.

  4. #4 Scott
    August 14, 2008

    Don’t worry. State and Federal agencies are pushing for mandatory GPS tracking of all vehicles in the US. Then not only will it be legal, you won’t have a choice.


  5. #5 Alex Besogonov
    August 14, 2008

    GPS receivers are EASY to detect.

    All modern receivers use supersonic heterodynes (http://en.wikipedia.org/wiki/Superheterodyne_receiver) which themselves emit radio waves (not much, but a detectable amount).

  6. #6 Foole
    August 14, 2008

    Hi Matt,

    Excellent article. A couple of things to point out.

    First, we think encryption is secure because we don’t know of any math that makes cracking a cipher easier. For instance, we don’t know of an easy way to do prime factorization (and by easy I mean that we don’t know of a way of doing the operation on large numbers so that it doesn’t take forever). It’s possible that the NSA knows of a weakness, but hasn’t reported it yet (this isn’t as paranoid as you may think — this has happened in the past, e.g., differential cryptanalysis). I’m not arguing against, cryptography, by the way. I just don’t want folks to think they’re 100% safe just because they have something encrypted. And more people should definitely be encrypting their private files.

    Second, even if GPS tracking were taken completely off the table, most people carry around a device that allows them to be tracked: a cell phone. Granted, tracking by cell phone is not as precise. But, cell phones don’t require that I have to surreptitiously attach a device to someone, either. Further, as an extra bonus the government can serve a warrant to the phone company and possibly turn your phone into a passive listening device. I’ve read a few articles of this very thing happening to some mafioso. If I wanted to spy on someone, I think I would go the cell phone route.

  7. #7 ParatrooperJJ
    August 14, 2008

    A low power GPS jammer (range of 25′) that plugs into the cigarette lighter can be easily obtained from a number of vendors.

  8. #8 stan
    August 14, 2008

    Placing a tracker on a car may constitute trespass to chattels (just as touching someone without permission can be a battery). And the damages are what? After the device is removed, there is nothing to recover.

    Do we have a reasonable expectation of privacy about where our car goes? I don’t think the courts are wrong here. The car can be observed by anyone as it drives along the street. Why does the driver or owner have an expectation of privacy regarding where the car goes?

  9. #9 Leo
    August 14, 2008

    Um, in Massachusetts you need a warrant. I’ll have to look at the the article to see if it says where you don’t.

    You can retrieve gps data from gps systems and even cell phones these days. Also with a warrant.

  10. #11 AST
    August 14, 2008

    “If something would be otherwise illegal, the police ought to have a warrant. Period.”

    Not quite. The Fourth Amendment protects us from unreasonable searches and seizures so it always comes down to the facts involved. Getting a warrant isn’t necessarily a safe harbor since since the defendant may still argue that the warrant was issued without probable cause and shouldn’t have been granted.

    The central issues are the type of intrusion involved, the extent of it, the degree to which the search incurs ones reasonable expectation of privacy, etc. I don’t know enough of the details to say whether this was a S&S violation, so I’ll leave it there.

    However, I don’t think the Fourth Amendment was intended to make us all prey to criminals. We seem to think there is something magic about a magistrate’s order, when many of these are just local JPs who have no better qualifications than the cops. As I say above, we should be looking at the overall reasonableness. Of course, any evidence seized will be reviewed by a court if a criminal information is filed, so it would be foolish for cops to cut corners that could jeopardize the prosecution, yet they do it far too often. I think this is due to the fact that the individual police officers seldom suffer any penalty other than the exclusion of their evidence. This makes no sense to me.

  11. #12 AtheistAcolyte
    August 14, 2008

    @ #7:

    A low power GPS jammer (range of 25′) that plugs into the cigarette lighter can be easily obtained from a number of vendors.

    Man, that might really piss off the guy in the car next to you, though…

  12. #13 Matt Springer
    August 14, 2008

    Man, that might really piss off the guy in the car next to you, though…

    And it’s an inconvenience to the driver himself if he uses a GPS navigator. I use one, and I have to admit that driving without it now feels like a step back to the stone age.

  13. #14 CCPhysicist
    August 15, 2008

    Matt wrote: “Keep this in mind when voting for state representatives and local judges.”

    You must be joking. Only one court matters, and that means you need to keep this in mind when voting for President. Period, end of story. Although in theory the Senate should also matter, history shows that the President can eventually get the court he wants. The degradation in our civil liberties in the last few years makes the situation in my youth (when the wiretaps were actually illegal) pale in comparison and your concern with GPS tracking seem naive.

    As for “bugging” your computer, that is much easier than you might imagine. I seriously doubt if a warrant is needed to listen to anything its electronics transmits beyond your private property. And do you really know what Microsoft or other companies have installed on your computer? Similarly, much can be inferred from the techniques of “signals intelligence” even if the data cannot be read. That might be enough to get probable cause for a warrant that would enable keystroke logging.

  14. #15 andy.s
    August 15, 2008

    New technology cases like this always go up the SCOTUS, but it’s a total coin flip how they’ll rule on it.

    Is it kind of like planting a microphone on a person, which needs a warrant? Well, kinda.

    Is it kind of like a high tech way of following you around in a car or helicopter, which doesn’t need a warrant? Well, it’s kinda like that, too.

    Your car’s movement around the city don’t really sound like your personal secrets. Your movements in public don’t really have an reasonable expectation of privacy.

  15. #16 Matt Springer
    August 15, 2008

    You must be joking. Only one court matters, and that means you need to keep this in mind when voting for President.

    Not so. SCOTUS sets limits, but any local jurisdiction may set their own stricter limits on tracking should they wish. For instance: DC v. Heller stated that while complete handgun bans were unconstitutional, it strongly suggested that prohibition of concealed carry would be constitutional. However, local jurisdictions can and do extend concealed carry rights even though SCOTUS doesn’t require it. In this particular GPS example, even if SCOTUS rules it’s perfectly kosher to track without warrants there is still at least one state mentioned in the article which requires warrants. Essentially, states may not restrict rights any further than SCOTUS allows, but they may extend rights further than SCOTUS requires.

  16. #17 CCPhysicist
    August 17, 2008

    But if you want to protect your personal rights in the face of the threat posed by legislators or local officials pandering to a fearful populace willing to trade their rights for the illusion of safety, the Constitution has more potential to protect you even if it was ignored when Jim Crow was the Law of the South and in some more recent events.

    Do you really want your rights to change when you cross the street into a different town? Do you think those local or state limitations apply to federal officers? They will just do it without a warrant if a warrant is not required in Federal courts.

  17. #18 Matt Springer
    August 17, 2008

    Agreed. The federal government and the Supreme Court in particular is a vital battleground for privacy and freedom. But no one should forget that it’s definitely not the only battleground.

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