On June 22, 2018 the Supreme Court of the United States (USSC) issued their long-awaited decision in Carpenter v. United States, 585 U.S. ___ (2018).  The majority opinion and four separate dissenting opinions cover nearly 119 pages.  The purpose of this article is to frame the issue and briefly summarize the decision with an emphasis on the ramifications of the decision with respect to law enforcement.

To understand the practical effects of this decision, we must understand two distinct Fourth Amendment concepts: The Third -Party Doctrine and Mosaic Theory.  Let me briefly summarize these two concepts to better frame the analysis of the decision that follows.

The Third-Party Doctrine is a Fourth Amendment principle primarily derived from two post-Katz USSC decisions: Smith v. Maryland, 442 U. S. 735 (1979) and United States v. Miller, 425 U. S. 435 (1976).  Basically stated, these two cases stood for the proposition that it was not reasonable to expect privacy in information voluntarily provided to commercial third-parties.  In Miller, this rule applied to banking records. In Smith, the doctrine was applied to telephone numbers being dialed.  As a result of the categorical application of what came to be called the “Third-Party Doctrine,” subpoenas and statutory court-orders have been used to obtain this information since such information did not receive Fourth Amendment protection under this doctrine.

Mosaic Theory is a little more complicated, but essential to understanding this decision.  Mosaic Theory stands for the proposition that certain types of warrantless surveillance over an extended period of time becomes unreasonable to continue without a warrant (at some undefined point).  The key Supreme Court decision that is referenced throughout the majority opinion in Carpenter is United States v. Jones, 565 U. S. 400 (2012). In Jones, although the majority opinion was not based on Mosaic Theory, in dicta five of the nine justices embraced the concept that extended position location surveillance through the use of GPS could create Fourth Amendment privacy concerns.  For the last six and a half years, lower courts have been wrestling with the application of Mosaic theory based on the dicta in Jones (most notably in cases involving extended warrantless video surveillance).

That brings us to the decision in Carpenter.

In Carpenter, the FBI used 2703(d) Orders to obtain historical cell site location information (CSLI) for the defendant’s cellphone from his cell service provider that provided nearly 13,000 location points over 127-day period.  Unlike Fourth Amendment search warrants, 2703(d) Orders are granted on a standard lower than probable cause.   At trial, the defendant argued that, under Mosaic Theory, this action constituted a search under the Fourth Amendment requiring a warrant based on probable cause.  The government countered that the Third-Party Doctrine applied and therefore it was not reasonable to expect privacy in the CSLI data gathered and maintained by the cellphone carrier. The Sixth Circuit applied the Third-Party Doctrine categorically in rejecting the defense’s motion to suppress.

The Supreme Court agreed to hear the case on appeal from the Sixth Circuit. In a 5-4 decision, the Supreme Court held that it was reasonable to expect privacy in the massive amounts of historical CSLI generated by cellphones when connecting to cell towers and retained by cell service providers. This was based largely in part on the Mosaic Theory concepts concerning location and movement information discussed in the 2012 Jones decision.  The court also, to a large extent, abrogated the Third-Party Doctrine by ruling that this rule of law is not categorical.  In other words, what used to be a “bright line” rule is no longer a bright line rule.  The court held that the Third-Party Doctrine does not apply to historical CSLI records and therefore the FBI needed a warrant to obtain historical CSLI.

This decision will make some criminal investigations more difficult for criminal investigators for at least two significant reasons.  First of all, it was often the CSLI that was obtained with 2703(d) Orders that helped uncover the criminal activity that often led to the basis of probable cause for search warrants that providing incriminating evidence. In other words, it was often the CSLI that helped establish very probable cause the Supreme Court is now demanding.  Second, the applicability of the Third-Party Doctrine is very much in question now that the rule is no longer a categorical or “bright line” rule.  The court emphasized that this decision was “a narrow one” limited to obtaining CSLI. However, as Justice Alito predicted in his dissent, “We will be making repairs – or picking up the pieces – for a long time to come.”  We certainly haven’t seen the last of the Mosaic concept.

This decision creates a lot of uncertainty for law enforcement, but this much is clear: Many serious criminal cases have been solved through the use of CSLI obtained with 2703(d) Orders.  In eliminating this criminal investigative tool, there will undoubtedly be no small number of cases that will go unsolved as a result of the Carpenter decision.  More importantly, this case could signal the beginning of the end of the Third Party Doctrine as it is applied to digital data stored by a commercial third-party.