I'm not a lawyer (constitutional law or otherwise), but my understanding of the reasoning behind Smith v. Maryland (full text) and the subsequent "third-party doctrine" was that:

  1. The phone companies know what number is dialed, and people know that because the phone company's equipment has to know where to route you.
  2. The phone companies keep a record of every call dialed, and people know that because they see it on their monthly phone bills.
  3. People know that "pen registers" and similar devices exist, or at least the technology to trace a call exists, because the phone company can track down people who make harassing calls.

    • Therefore, people shouldn't reasonably expect the numbers they dial to be private.

From the opinion:

Telephone users, in sum, typically know that they must convey numerical information to the phone company; that the phone company has facilities for recording this information; and that the phone company does in fact record this information for a variety of legitimate business purposes. Although subjective expectations cannot be scientifically gauged, it is too much to believe that telephone subscribers, under these circumstances, harbor any general expectation that the numbers they dial will remain secret.

What I'm wondering is whether there's any subsequent case law which questions whether the third-party doctrine holds when one of these tests is not true. I'm specifically interested in cases where #2 is violated, although I'd be interested in the others as well (e.g. a hypothetical secret machine that can read the contents of mail without opening the envelope).

My entirely untrained (and only moderately informed) opinion would be that because ISPs don't make it obvious in any way that they keep a record of what you do online (your monthly bill isn't broken down by website, for example), then the third-party doctrine shouldn't be applicable to them. Likewise, until Snowden brought attention to it, I would have expected most people to not know that their activity could be easily intercepted. Since there haven't been any cases making this point that I've heard of, I assume that either the cases have been quiet or there's a flaw in my logic and thus no one has tried.

1 Answer 1


You've identified exactly the right question: whether the person's subjective expectation of privacy, when viewed objectively, is the "justifiable under the circumstances". (Smith v. Maryland)

The Supreme Court hasn't addressed how this test applies to ISPs and website requests. However, this question has been addressed by several circuit courts of appeal. I'll build a list of example cases. Many find that there is no reasonable expectation of privacy in this information, but there are some cases that go the other way, and there is some nuance regarding exactly what information is being given away.

US v. Beckett (11th Cir. 2010):

the information consisted of the identifying information transmitted during internet usage and phone calls that is necessary for the ISPs and phone companies to perform their services. It is unreasonable for Beckett to have been unaware that such information was being transmitted to the ISPs and phone companies and so he “assumed the risk that the company would reveal to police the [information].”

United States v. Forrester, 512 F.3d 500, 510 (9th Cir. 2007):

Analogously, e-mail and Internet users have no expectation of privacy in the to/from addresses of their messages or the IP addresses of the websites they visit because they should know that this information is provided to and used by Internet service providers for the specific purpose of directing the routing of information. Like telephone numbers, which provide instructions to the "switching equipment that processed those numbers," e-mail to/from addresses and IP addresses are not merely passively conveyed through third party equipment, but rather are voluntarily turned over in order to direct the third party's servers.

Regarding your secondary question about a "secret machine" that the government develops to get access to contents of an envelope without opening it, that is very similar to the situation in Kyllo v US 533 U.S. 27 (2001) (internal quotations removed):

[...] obtaining by sense-enhancing technology any information regarding the home's interior that could not otherwise have been obtained without physical intrusion into a constitutionally protected area constitutes a search-at least where (as here) the technology in question is not in general public use. [...] Reversing that approach would leave the homeowner at the mercy of advancing technology-including imaging technology that could discern all human activity in the home.

  • Thank you for this answer. One question, though. You mention that there are some cases that went the other way, but you don't reference one. Is there an actual circuit split, or have they just addressed different aspects of it?
    – Bobson
    Dec 8, 2016 at 14:50

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .