Yesterday, in United States v. Diaz-Castaneda, the Ninth Circuit had some interesting dicta in an otherwise-routine Fourth Amendment decision. The dicta touches on a topic that law professors have long been very interested in, so I thought I would flag it.

  The facts of the case are simple. A police officer saw a truck driving on the highway, observed its license plate number, and then ran a computer check of the plates and learned that the registered owner of the truck had a suspended license. The officer saw that the driver of the truck matched the description of the owner of the truck, so he pulled over the truck. The issue in the case was whether the officer's viewing the plates and running the computer check was a Fourth Amendment "search" of the driver that occurred without probable cause and was therefore unlawful.

  In an opinion by Judge Fisher, the court concluded that no search occurred: the license plates were in plain view, so the officer did not search or seize anything by seeing the tags. This is clearly right in light of cases like New York v. Class. But then the court did something unusual; it adopted parts of a framework from a 6th Circuit dissent suggesting that license checks could be searches in some cases because they might retrieve particularly sensitive information.

  In Diaz-Castaneda, the Ninth Circuit concluded that the license check in this particular case was not a search, but that other checks might be searches in some cases:

[T]here is no indication that license plate checks in Oregon result in the retrieval of information that "may not otherwise be public or accessible by the police without heightened suspicion." The information that [the officer] accessed about [the driver], namely that he was the registered owner of the truck and that his license was suspended, was already present in the police database and presumably available to any inquiring police officer. Were this not the case — for example, had [the officer] used [the driver]'s license plate to obtain information that [the driver] reasonably expected would be unavailable to the police, or had [the officer] violated police guidelines regarding the proper searching of databases — our conclusion might very well be different.

  This suggestion is just a suggestion, and obviously doesn't settle anything. But it's hinting at a pretty revolutionary idea. The Fourth Amendment has always been understood to regulate government collection of information but not subsequent use of information. Once information is collected, the government is free to use it however it wants. But here the Court seems to be suggesting a potential use restriction. First, license check "might very well" be a search if the officers do not comply with "police guidelines regarding the proper searching of databases." Second, it might be a search if the information retrieved by the officer is information that a driver wouldn't reasonably expect an officer to be able to retrieve (which I gather refers to information in government databases held outside the police department, although it' not clear).

   I'm understanding the language correctly, the panel seems open to the idea that that the government might collect information without violating a reasonable expectation of privacy -- leading to its inclusion in some kind of government database -- but then could retrieve the information in a way that does violate a reasonable expectation of privacy. That is, the court seems to be suggesting the possibility of a Fourth Amendment use restriction beyond the rules regulating the initial government collection of information. This is a pretty revolutionary suggestion, and I'll be very interested to see if a future Ninth Circuit panel takes that ball and runs with it.

  Thanks to Howard for the link.