Sunday, April 23, 2006

Tracking devices

The Fourth Amendment is the constitutional provision that protects citizens from having their privacy arbitrarily invaded by the government. The Fourth Amendment requires the government to get a warrant or invoke an exception to the warrant requirement before it can invade your privacy by, say, searching your home or office.

In my posts "Cartapping" (February 12, 2006) and "Can You Trust Your Car?" (April 19, 2006), I talked about the extent to which the Fourth Amendment applies to the government's using technology installed in your vehicle to eavesdrop on what you say while in the vehicle.

In this post I want to talk about something different: whether the Fourth Amendment applies to the government's using computer technology to track your movements in public areas. Until relatively recently, the only way the government could do this was to have police officers follow someone, and the Supreme Court has held that following someone is not a "search" under the Fourth Amendment. Searches invade a reasonable expectation of privacy, and it is simply not "reasonable" to say that my driving down city streets or on a highway is "private," since anyone who happens to be in the area, or who is inclined to follow me, can where I am and infer where I am going. And in United States v. Knotts, 460 U.S. 276 (1983), the Supreme Court held that it was not a "search" for law enforcement officers to use a beeper installed in a vat of chemicals to follow a car; the vat was in the car, and the signal it transmitted helped the officers to follow the car to its final destination. All the beeper did was to send out an audible signal that became stronger when the officers were closer to the car and weaker as they fell behind.

Beepers have become antiques. Today, police use one of two techniques to track someone's movements:
  • Use an individual's cell phone to track her movements: If the cell phone is on (and maybe even if it is not), the cellular phone service provider can tell where the person carrying the cell phone is. This can be done in two ways: The older method is to use signals from cell phone towers to identify where a particular cell phone is located; cell phones continually send out registration messages to cell phone towers in the area. It is possible, using a technique called triangulation, to use these messages to pinpiint the location of a specific cell phone, and track its movements. The newer method is to use GPS receivers installed in the cell phone; several years ago, the Federal Communications Commission mandated that, by the end of 2005, new cell phones have GPS technology installed. The purpose was to make it easier to find someone who had been injured in say, a car accident, and could call for help but could not explain where he was.
  • Install a GPS tracking device on someone's vehicle and use it to track her movements: The tracking devices are small, and can easily be installed on a vehicle without the owner's knowing it. Unlike the beeper at issue in Knotts, they do more than simply send out a signal that helps humans follow a vehicle. GPS devices track a vehicle's movements automatically, sending the information to a receiving unit in a police station or other central facility. This means, of course, that no officer actually has to follow the vehicle; the GPS device automates the process. It also means, as some courts have noted, that the process of tracking the vehicle is vastly improved; the GPS device tracks the vehicle's movements on an uninterrupted 24/7 basis for as long as it is installed . . . for weeks, say. As some judges have noted, this type of tracking is realistically impossible for law enforcement agencies with limited resources.
The issue that is currently being litigated by federal prosecutors, privacy advocates and defense attorneys is whether the use of either of these tracking techniques constitutes a "search" under the Fourth Amendment. If it does, then the agents who want to use one of the techniques must obtain a search warrant from a duly authorized magistrate, and must ensure that the tracking stays within the scope of the warrant. If it does not, then the agents may have to get an order from a court authorizing the installation and use of the device, but they will be proceeding under statutory provisions that are far less demanding than the Fourth Amendment.

These tracking techniques illustrate a major problem we are facing with regard to privacy: How do we maintain the balance between privacy and legitimate law enforcement activity in the face of rapidly-evolving technology?

As I noted above, the only Supreme Court case on point for the use of these tracking techniques is Knotts . . . a 23-year-old decision that dealt with comparatively primitive technology. We do have, as I also noted, a number of decades-old federal statutes that establish processes agents must use to, for example, have a telephone company install a device that captures the numbers dialed from a phone, but they really do not apply to the use of cell phone GPS technology.

Nor is it clear whether the installation of a GPS tracking device on a vehicle is constitutional under Knotts. As I said, the use of such a device clearly results in the collection of information that far exceeds what a typical police department could accomplish by using human resources. Courts are struggling with whether that takes the use of a GPS tracking device out of the holding in Knotts and transforms it into a Fourth Amendment "search" that can only be conducted with a warrant.

So, what should we do? How should we resolve these issues?

Traditionally, we would (a) wait until the issue had made its way through the lower courts to the Supreme Court, which would issue a definitive opinion; and/or (b) adopt legislation that dealt with the problem. (Congress has, in this general area, tended to adopt statutes that implement and sometimes exceed the requirements of the Fourth Amendment.)

There are two problems with following this traditional approach in an era of rapidly-evolving technology:
  • It can take forever for a case to make its way to the Supreme Court, be argued, and then decided. (And this Supreme Court takes very few cases -- roughly 75 a term, I believe.) If that decision enunciates a broad standard, then that standard can be extrapolated to help us deal with issues other than the specific issue (and technology) that went to the Court. But if the Court issues a very limited decision, that decision, and this whole process, will be of little help as we attempt to sort out the rapidly emerging legal issues generated by new technologies. The Court did precisely this, i.e., issued a very limited decison, in Kyllo v. United States, its 2001 pronouncement on the Fourth Amendment's applicability to law enforcement use of technology. In Kyllo, the Court was asked to decide if the use of a thermal imager to detect heat emanating from a structure is a Fourth Amendment "search." In a majority opinion written by Justice Scalia, 5 Justices said it was. More precisely, they said it is a "search" (i) to use technology that is not in general public use to (ii) detect information from inside a home, information an officer could not get otherwise except by going into the home. This holding is limited and inherently ambiguous (what happens when technology is in general public use? what happens if it's not a home?) . . . which means it is of little assistance in sorting out issues generated by law enforcement's use of evolving technologies. Unless the Supreme Court changes its approach to deciding cases like Kyllo, this alternative is not likely to be particularly helpful in resolving the dilemma I am writing about today.
  • It can take a very long time (maybe not forever) for a legislature (Congress or a state legislature) to adopt statutes that address issues such as the cell phone or GPS tracking. And when a legislature does act, it tends to adopt technologically-specific legislation . . . like the statute I mentioned above, the one that governs the use of a device that captures the numbers dialed on a traditional landline phone. This, of course, means that the statute may well be out of date by the time it goes into effect.
I am not going to propose a solution to this problem today. This happens to be the area in which I am currently writing; I have a very long law review article coming out that deals with these and other issues generated by our need to apply legal standards to new technologies. I will try to summarize that article in another, later post.

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