Gathering versus Mining Evidence: DNA, heat waves, garbage, and urine

by Sherry F. Colb

My column for this week, part one of a two-part series on Justia's Verdict, examines the case of Maryland v. King, in which the U.S. Supreme Court heard argument on February 26th.  The case asks the question whether taking DNA from people who have been arrested, in the absence of any individualized suspicion to support DNA sampling, violates the Fourth Amendment right against unreasonable searches and seizures.  One of the questions that arose (but went unresolved) during oral argument was whether the Fourth Amendment might impose requirements on the government if it has collected discarded DNA (from a cup that the suspect had used to drink water, for example) and wishes to analyze the DNA for some or all of the information contained within it.  The attorney representing Alonzo Jay King suggested that such an analysis of DNA would count as a Fourth Amendment "search" and would accordingly require justification.

In this post, I want to consider this question, because it has long had a very clear answer from the doctrine, but the doctrine may (appropriately) be in the process of changing.

In the case of California v. Greenwood, the question arose whether police could, without a warrant or probable cause, examine a suspect's garbage, left for collection at the curb in a sealed, opaque bag.  The U.S. Supreme Court said yes, police could examine such garbage, because -- among other things -- a person who leaves garbage at the curb for collection has voluntarily relinquished the garbage to a third party and has thereby given up any reasonable expectation of privacy in that garbage.  In another case, United States v. Miller, the Court held that the government may subpoena an individual's bank records without triggering any reasonable expectations of privacy, because a person with a bank account has voluntarily shared the information contained in these records with third parties -- the bank.  And in Smith v. Maryland, the Supreme Court said that police do not trigger the Fourth Amendment's requirements when they ask the telephone company to hand over the phone numbers that a customer dialed, because, again, a person with a telephone account necessarily shares the numbers that he or she dials with the telephone company and thus retains no reasonable expectation of privacy against its disclosure.

The basic rationale for each of these cases is that when people relinquish private property or private data to a third party, they simultaneously forfeit any privacy interest they previously had against the government's examining that property or data.  If this rationale applies to DNA, then police could thoroughly analyze everything contained within an individual's discarded DNA without having to offer any preexisting suspicion of the individual and without having to have any legitimate reason for analyzing his DNA.

In an article published in the Stanford Law Review in 2002, What is a Search: Two Conceptual Flaws in Fourth Amendment Doctrine & Some Hints of a Remedy, I argued that people ought to be able to share their private matters with selected third parties without thereby forfeiting an interest in the matters remaining private, for Fourth Amendment purposes.  In a concurring opinion in United States v. Jones, Justice Sotomayor hinted at the possibility that she might be ready to revisit some of the older cases, on a rationale that nicely tracks the arguments I made in my article, as I discussed in a two-part series of columns about Jones, here and here.  But even without this hint, there is some evidence in recent case law  that the "voluntarily relinquished" rationale is running out of steam.

Take, for example, the case of Kyllo v. United States.  In this case, the Supreme Court held that the Fourth Amendment prohibits police from using a thermal detection device to analyze the heat patterns emerging from a private home, in an effort to find out whether a suspect is growing marijuana inside his home.  Even though the device in question measured only heat waves that had already made it out of the private home -- waves that could accordingly be characterized as "abandoned" by the resident -- the fact that the device served to expose private matters that would otherwise remain undetected renders its use a "search" for Fourth Amendment purposes that must accordingly be justified.

Justice Stevens dissented in the case, noting that the device at issue did not perform any "through the wall" surveillance but only "off the wall" surveillance -- i.e., it did not actually penetrate the walls of the home but merely gathered heat discarded into the out doors.  Yet a majority rejected that argument and even implied that the distinction between "through the wall" and "off the wall" amounted to an exercise in sophistry and formalism.

And in the same year, in Ferguson v. Charleston, the Supreme Court held that police had "searched" women, for Fourth Amendment purposes, by asking medical professionals who were  delivering the women's babies to collect urine from their patients during delivery and then analyze the urine for the presence of cocaine, passing along the resulting evidence to the police.  Despite the fact that the women had plainly discarded their urine, the Court nonetheless regarded police analysis of the resulting data as an invasion of the target's reasonable expectation of privacy.  Though the women parted with their urine, they did not thereby relinquish their right to privacy from criminal law enforcement officials in the information contained within that urine.

Then in United States v. Jones, mentioned above, the Court held that using a GPS device to track the whereabouts of an individual's car on the public roads for a month triggers the protection of the Fourth Amendment right against unreasonable searches.  The majority relied on the trespass involved in placing the GPS device into the car.  However, at least five Justices (four in dissent, and one in a separate concurrence after joining the majority opinion) indicated their belief that what makes the use of a GPS a "search" has at least as much to do with the invasion of privacy involved in revealing all of the places where an individual has traveled in the course of a month, as it does with the (trivial) trespass involved in attaching the small GPS device to the suspect's vehicle.  In other words, even though a person voluntarily exposes himself to public viewing by driving on the public roads (and thereby relinquishes control of that information), the accumulation and analysis of data that becomes possible with a GPS nonetheless represents an unwarranted invasion of Fourth Amendment privacy.

In all of these cases, we see the shrinking of the previously-robust doctrinal distinction between physically gathering a piece of evidence (or physically invading private space to obtain information), on the one hand, and examining that evidence closely for all of the information it holds, on the other.  Returning to Greenwood, the garbage case, one might see Kyllo, Ferguson, and Jones as supportive of the argument that just because you have relinquished a bag of garbage does not mean that you have given up your legitimate interest in the secrecy of the personal facts contained within that garbage.  The legitimacy of the government's having custody of a bag of garbage, for example, because it has taken it from the curb, does not necessarily entail the legitimacy of rifling through that garbage.  And for similar reasons, "abandoning" one's DNA on a discarded water glass may not necessarily entail a relinquishment of one's interest in the secrecy of the information contained within that DNA.

Perhaps the Fourth Amendment's promise in the age of technology will reside in protection against the mining of data and the analysis of physical evidence, even when the law does not guard against the initial physical gathering of the data and physical evidence at issue.