Editor's note: The contestants were given free rein for their second post of the day. You can read Paul Rosenzweig's earlier post here.

The other day Yasir Afifi took his car in for servicing.  The mechanic found a stray wire attached to a magnetic device that he didn't recognize.  They pulled the thing from the car and posted pictures of it on the internet, asking for someone to help them identify the component.

Two days later the FBI showed up.  The device was theirs.  It was a GPS tracker that had been attached to Afifi's car.

Of course this isn't about Afifi.  At this juncture nobody knows whether or not the FBI had a good reason for putting a GPS on his car.  And, actually, that's exactly the point.  Nobody knows.  At least nobody outside of the FBI.

Why that is so is the product of a number of small, incremental steps in the law.  Each one, individually, makes sense.  Taken together, maybe they don't. 

Let's start with one of the basic tenets of Fourth Amendment law:  The Constitution protects only what you reasonably expect to be private, not what you voluntarily do in public.  So what you do in the privacy of your own home is one thing; what you do on the streets, something altogether different.

As a consequence, in general, the police do not need a warrant (that is, approval from a neutral judge before they act) to observe what you do in public.  In a lot of ways that makes sense--the cop walking on the street shouldn't have to get a warrant to watch someone walking on the other side of the road.  And the way that principle has worked itself out, that also means that the police don't need a warrant in order to follow your car on the street when you go for a drive.  That's why McGarrett and Dano don't need a judge's permission to tail a suspect - they just do it.

More than 25 years ago, in a case called Knotts, the Supreme Court took the next logical step.  If the police could follow you visually, they said, then there was nothing wrong with them using a little electronic helper to make it easier to follow you.  In Knotts, the police had put a primitive electronic beeper in a barrel and then tracked the barrel when it was picked up.  Knotts argued that the trackers needed a warrant and court approval to put the beeper in the barrel but the Court said that since the car with the barrel in it was traveling on a public street and could have been observed visually, the fact that the police used a beeper made no difference.

By now, you probably know how the story seems to end:  The technology has changed --  from a beeper to a GPS tracker - but the principle remains the same.  The reason only the FBI knows why it put the tracker on Afifi's car is because they didn't have to get permission from a judge before they did it.  And the reason they didn't need the judge's permission is because Afifi does not have an expectation of privacy in the movement of his car on the open roads.

But is that really how it should end?  Sometimes a difference of degree becomes a difference in kind. 

The good news is that maybe, just maybe, our courts are beginning to recognize that difference.  Recently, the D.C federal court of appeals held that the police had to obtain a warrant before installing a GPS tracker on a car and recording all his movements for a month.  In a case involving Antoine Jones [Full Disclosure:  I'm providing some pro bono assistance to Jones' counsel in this case], Judge Douglas Ginsburg observed:  "[U]nlike one's movements during a single journey, the whole of one's movements over the course of a month is not actually exposed to the public because the likelihood anyone will observe all those movements is effectively nil."  The state high courts of New York, Washington and Oregon have reached the same conclusion and also required warrants.

Most of the federal courts, however, have rule that the GPS tracker is just like the beeper.  They are wrong, I think. As another federal Judge, Alex Kozinski said (albeit without convincing enough of his colleagues), GPS tracking is different:  "You can preserve your anonymity from prying eyes, even in public, by traveling at night, through heavy traffic, in crowds, by using a circuitous route, disguising your appearance, passing in and out of buildings and being careful not to be followed. But there's no hiding from the all-seeing network of GPS satellites that hover overhead, which never sleep, never blink, never get confused and never lose attention." 

This is truly a case where the changing technology really requires a changed law.  It looks like the Supreme Court may weigh in soon and what they say will make all the difference in the world.

Read more entries from this challenge round. And come back Friday to vote.

By Paul Rosenzweig  |  October 19, 2010; 12:12 PM ET  | Category:  Blogging Challenge
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