The Mosaic Theory

By David K. Shipler
(published on the Web site of the American Constitution Society)

The Supreme Court has an opportunity next term to play catch-up in applying the Fourth Amendment to the advanced technology of surveillance. The Court has granted the Obama administration’s cert. petition seeking to overturn a well-reasoned opinion by the Court of Appeals for the D.C. Circuit requiring law enforcement to obtain warrants when secretly installing GPS tracking devices on vehicles.

This could be a mundane case or a landmark, depending on which way the justices go.
 The Fourth Amendment has been seriously eroded in recent decades, as documented in my book The Rights of the People: How Our Search for Safety Invades Our Liberties. The Court’s majority could continue the pattern by ruling with the government, carving out yet another exception to the warrant requirement. Or, the Court could decide to set broad new standards to redefine the “reasonable expectation of privacy” in a digital age.

The expectation of privacy is a key legal concept. The courts have ruled that where no such expectation exists, no “search” within the meaning of the Fourth Amendment occurs, and therefore no probable cause or judicial oversight is required.

A driver on public roads has no expectation of privacy, for example, because he can be observed by anyone. Therefore, longstanding precedent holds that a police officer needs no warrant to follow him. The Obama administration argues that GPS is nothing more than an electronic police officer recording a vehicle’s movements in public places, and that no warrant should be demanded, even for prolonged monitoring.

This view has been accepted by the 7th and 9th Circuits but not by the D.C. Circuit, which concluded that the quantity of information collected affects its quality. “Even though each individual movement is exposed” to the public, the three-judge panel ruled, “that whole reveals more—sometimes a great deal more—than does the sum of its parts.” Even where individual pieces of information are not covered by the privacy expectation, the judges decided, there may be an expectation of privacy in the complete picture generated by technology.

“It is one thing for a passerby to observe or even to follow someone during a single journey as he goes to the market or returns home from work,” the panel wrote. “It is another thing entirely for that stranger to pick up the scent again the next day and the day after that, week in and week out, dogging his prey until he has identified all the places, people, amusements, and chores that make up that person’s hitherto private routine.”

In this case, United States of America v. Antoine Jones, a suspected drug dealer was tracked by GPS 24 hours a day for four weeks, a duration that took the surveillance to an intrusive level, the judges found. “A person who knows all of another’s travels,” they wrote, “can deduce whether he is a weekly church goer, a heavy drinker, a regular at the gym, an unfaithful husband, an outpatient receiving medical treatment, an associate of particular individuals or political groups—and not just one such fact about a person, but all such facts.”

This is the “mosaic theory.” The government has used it many times to justify its own secrecy, arguing that if bits of information were released, they could be assembled by enemies into a mosaic portraying intelligence sources and methods. That was the Bush administration’s argument for keeping secret the names of more than 1,200 U.S. residents picked up and jailed for months after 9/11. It has been cited by the Obama administration in moving to dismiss civil suits by people who believe they have been targeted by secret surveillance. And officials use the mosaic theory to explain their secret collection of data on large numbers of Americans and foreigners, aimed at piecing fragments of information together.

Now that the D.C. Circuit has turned the mosaic theory around to protect the privacy of the individual, the concept could be applied to other warrantless monitoring. This could be done by the Supreme Court, which has always been slow to adjust to changing technology, by repairing two flaws in the case law.

First, the justices could use the mosaic theory to set limits on the computerization of searches without warrants by requiring probable cause and a judge’s signature before massive data acquisition on an individual.

Second, it could expand the expectation of privacy to include information given digitally to others—bills paid, books purchased, phone numbers called, e-mail addresses contacted—in recognition of the fact that you cannot live normally today without leaving an electronic trail. You should not lose control of personal information just because you convey it to your bank, phone company, and Internet provider. Government should need proper warrants to get it.

Fourth Amendment law needs updating. Will the Supreme Court take this opportunity?