This post was also written by Frederick Lah.

Last week, the New Jersey Appellate Division affirmed a lower court’s decision that a defendant did not have a reasonable privacy interest in his cell phone number. Defendant was a middle school teacher who had a sexual encounter with a student when the student was 13 years old. A conversation between the teacher and the student was set up and taped by the police, after a local officer obtained the cell phone number from the school’s principal. Defendant objected that he had a reasonable expectation of privacy in his cell phone number and that the state could acquire it only with a warrant.

The court ruled that a telephone number could be protected in some circumstances, but that here, the defendant retained no reasonable privacy interest. The holding was based, in part, on the fact that the defendant exhibited no surprise the victim had his number and that the defendant had in the past disclosed his number to the middle school community, i.e., he provided his telephone number to students and their parents previously in connection with a field trip, and he provided his number for an internal school staff directory. Once disclosed to these discrete communities for those stated purposes, the cell phone lost its status as private information.

The court’s common-sense ruling stands in tension with other quickly developing threads of privacy law. Increasingly, companies are being required to tell consumers more about the uses to which their information will be put. The burden on companies to provide “use specification” in ever-growing detail obscures the basic truth that information widely shared is not private. The defendant here made the previous disclosures with the understanding that they would only be used in connection with the field trip and for the internal directory, not for law enforcement purposes. Defendant never consented to having his cell phone number disclosed for law enforcement purposes. But by frequently sharing his cell phone number, he divested himself of the right to object to further sharing, including with the police.

These issues fall in line with previous discussions we’ve had on this site about this concept of public privacy. Those discussions can be found here and here. Previously, we asked whether the fact that we lose some privacy when we’re in public places means that we should be subject to being recorded with the possibility that the recording be widely publicized on the Internet. Here, we see an analogous line of questioning play out in the context of personally identifiable information. Does the fact that personally identifiable information is voluntarily disclosed to some members of the public mean that the information loses its privacy interest, even if the information is subsequently used for a different purpose for which it was originally disclosed? The court’s decision here provides at least one perspective on the issue.