My colleague Eric Posner has this criticism of the Supreme Court’s decision in Riley:

The court applies a balancing test in Fourth Amendment cases, under which the police can search a person without obtaining a warrant if the degree to which the search intrudes upon privacy is less than the degree to which the search is needed for a legitimate government interest—typically, in catching criminals and protecting police from danger.

How exactly does this court know how significant the privacy interest is? Many people don’t care much about their privacy; others do. Maybe those who care a lot don’t put personal information on their cellphones, or they ensure that it is encrypted or otherwise protected. Or they put information on their cellphones that you or I might consider personal but they don’t. Indeed, technology is not the only thing in flux here; so are social norms and personal beliefs about what information it is appropriate to share and what information should be kept to oneself.

And if the justices know what a smartphone is, they don’t know what these norms and beliefs are, and certainly not for the great mass of the population younger than they are, who have grown up with smartphones, Facebook, personal blogs, the Web. The court doesn’t seriously try to figure out how much people are really injured if a police officer looks at information on their cellphones. To do so, one would need to engage in a massive amount of empirical investigation, using surveys, focus groups, and market research—the stuff of committee hearings before legislatures. One senses, as is so often the case, that the justices are relying on their own personal experiences. They are thinking about what’s on their cellphones and how they would feel if a police officer saw them. As for the rest of society, we’re as opaque to them as DNA.

I agree with Eric that despite their personal experiences, their ability to talk to their law clerks, the research abilities of the Supreme Court librarians, etc., the Justices probably don’t have a deep knowledge of popular attitudes toward various kinds of privacy or intrusive police practices. But unlike Eric, I am not so sure that this is a problem, because I am not so sure that the Court is asking the question he thinks they are asking (or should be asking).

The criticism seems to presume that the Court is (or should be) engaging in some form of subjective welfarism, where the “intrusion” side of the balance depends on people’s subjective norms and beliefs about how bad the intrusion is. But I don’t think that the Court’s Fourth Amendment precedents quite work that way. Rather, they simply assume that privacy is valuable because the Fourth Amendment says so, and it is one of “the protections for which the Framers fought.”

Another way of putting this, I think, is that the Supreme Court’s cases appear to agree with Orin that the Fourth Amendment’s reasonableness inquiry “is normative, not descriptive.”

Now the Court does still have to inquire how much private information about you has been gathered, and maybe even whether that exposure is important in some sense, but those judgments aren’t subjective welfarist judgments. What else could they be? Well, to a large extent the Court seems to reason by analogy from its past precedents and other historical fixed points.

The same thing happens, I think, in other constitutional balancing tests such as strict or intermediate scrutiny. When the Court decides that the Constitution permits a ban on material support for terrorism, but not a ban on flag-burning, it isn’t making a judgment about how much people care about supporting terrorists or burning flags. It’s simply fitting the new cases into the old pattern of things the Court has already said are okay or not okay.

Hence, rather than surveys, the Court relies on analogies like these:

Most people cannot lug around every piece of mail they have received for the past several months, every picture they have taken, or every book or article they have read—nor would they have any reason to attempt to do so. And if they did, they would have to drag behind them a trunk of the sort held to require a search warrant in Chadwick rather than a container the size of the cigarette package in Robinson.


Indeed, a cell phone search would typically expose to the government far more than the most exhaustive search of a house: A phone not only contains in digital form many sensitive records previously found in the home; it also contains a broad array of private information never found in a home in any form—unless the phone is.

So there is a balancing test going on, but it’s a balancing test whose inputs are partly normative and historical, rather than subjective. Obviously those who think the Supreme Court should be trying to maximize national welfare rather than to apply historical principles to new circumstances won’t approve of that. But I do think my account is a better account of the Court’s project, and an explanation for why the Supreme Court library isn’t doing surveys, focus groups, or market research.

[Incidentally, Eric’s post is part of Slate’s “Supreme Court Breakfast Table," but, he writes: “Here’s a bit of inside information: there is no breakfast table. I ate by myself this morning in my kitchen." Eric and I did argue about this case at the lunch table, though. A real lunch table.]