In her concurring opinion in US v. Jones, 565 U.S. ___ (2012), Justice Sonia Sotomayor brought up a crucial point regarding a democracy's natural acceptance or resistance to government surveillance. As you may recall, the Court in Jones addressed whether the government's attachment of a GPS tracking device to someone's car in order to continuously monitor their movements constitutes a search or seizure under the Fourth Amendment. Jones is particularly significant in contemporary Fourth Amendment jurisprudence, as it considers the potentially corrosive effects that contemporary developments in surveillance-enabling technologies can have on a society.
In her brief, but powerful, concurrence, Justice Sotomayor observed that rapid advances in technology--making devices smaller, more powerful, and more energy efficient--give the government an advantage by creating new surveillance techniques that may not fall under the increasingly anachronistic "reasonable expectation of privacy" test found in Katz v. U.S. Observing that these advances in surveillance technologies and procedures may significantly tip the existing balance in the government's favor, Sotomayor identifies two "ordinary checks that constrain abusive law enforcement practices: limited police resources and community hostility." (citations omitted). This observation has always struck me as a perfect articulation of the dangers society faces when technology allows the state to cheat on this exam by refusing to sit for it in the first place.
This observation by Justice Sotomayor, which I will refer henceforth as the Sotomayor Surveillance Scale, brilliantly illustrates the historically natural resistance posed to government surveillance programs by limited resources and public opinion (see Fig. 1). As shown in Figure 1, these two factors are represented on two axes.
The x-axis, labeled "Notoriety," reflects how well-known or observable a surveillance program is, thus opening it up to public scrutiny and possible disapproval. The y-axis, labeled "Infeasibility," shows how practical (or impractical) a surveillance program is due to increased requirements, resulting in a natural resistance based on resource availability.
To better explain the Sotomayor Surveillance Scale, I shall borrow a hypothetical from former Chief Justice Rehnquist. In a 1974 Kansas Law Review article, Rehnquist asked the question "Shall the government keep a dossier of information pertaining to every citizen?" Acknowledging that this sort of program would not be tolerated by the public, he gives the following example. Suppose a police department decides to park a patrol car at the entrance to a popular bar every evening for the purpose of recording the license plate of every car that enters and leaves the bar's parking lot. Before long, the police department would be able to compile a reasonably accurate database of people who happen to frequent this bar. If we assume that the bar in question has all the necessary licenses, and there is nothing otherwise untoward going on in this establishment, Rehnquist observes that the great majority of people would object to this activity, and would say that this is not a proper police function.
Chief Justice Rehnquist gives two possible reasons for this objection. First, because the bar's patrons--and anyone else who happened to pass by the area--could easily observe the police behavior, and would resist the government's attempt at creating such a database. In Figure 2, this behavior is illustrated on the x-axis, where at some point (x*), the surveillance activity becomes sufficiently well-known (or notorious), and the potential for public resistance to such a program begins to increase.
Rehnquist's second reason for resistance comes from public disapproval due to inefficient use of police resources. In Figure 3, this is represented along the y-axis, where at some point (y*), the surveillance activity becomes too resource-intensive, and people may begin to complain that their tax dollars could be better spent.
Therefore, when a government surveillance program is both highly visible and highly infeasible, as shown in Figure 4, the likelihood of such a program passing public scrutiny decreases significantly. You will notice, however, that there is a zone in the Sotomayor Surveillance Scale where resistance will become light (or nonexistent), due to a program's low public visibility, its low cost, or both. This is the sweet spot that advances in surveillance technologies give the government the opportunity to shoot for. The government cannot simply open and inspect every package or read every piece of (physical) mail without such a program becoming widely known by the public, and quickly rejected as excessive surveillance. (N.B. The East German Stasi made an impressive attempt at such a program, but their public resistance was minimized by unacceptable means.) If, however, the government is presented with sufficiently fast processors and sufficiently expansive storage capabilities, a program to open and read every single (unencrypted) electronic communication without anyone in the public knowing about it becomes a possibility.
Similarly, a physical mail surveillance program would quickly become infeasible, given the vast amounts of personnel, physical space, and infrastructure required for such an activity. But as the price of advanced processors and digital storage continues to fall, and as automated textual analysis algorithms get better, the resource costs drop to a point where a government would be foolish not to consider such a program.
I was reminded once again of the Sotomayor Scale, and how government agencies are tempted aim for a point of least resistance on that scale, by the recent story of widespread use by police departments of powerful cellphone signal interception devices, some known by their brand name of stingray. These devices allow their user to track cellphones by mimicking a valid cell tower, thus capturing cellphone signals without their owner's knowledge (or permission). The government's stated purpose behind the use of such advanced devices is to thwart only the most dangerous criminals and terrorists, but police have found the device can be just as useful to catch petty offenders, since the vast majority of us now carry cellphones. The problem (for government) is that many courts require law enforcement agencies to obtain a search warrant before using the technology, and the probable cause necessary to get such a warrant just isn't there.
So how do government agencies move the use of stingray technology to the Sotomayor Scale sweet spot? Simple: they just keep its use a secret, and use the results (which would not be admissible as evidence without the aforementioned warrant) to establish probable cause through parallel construction, and if that doesn't work, just drop the case.
This recent example of government use of advanced surveillance technologies to cheat on the Sotomayor Scale is just one of many, which is why we should all read and understand the full import of Justice Sotomayor's precient observations.