Earlier this week, the Supreme Court heard oral argument in Rodriguez v. United States, a case on the allowed length of traffic stops. I didn’t make the argument in person, unfortunately, but the transcript has been posted. Here’s a reaction based on the transcript.

The notable aspect of the argument is that the Justices were more interested in the broad issue of how long traffic stops can last than the narrow question raised in the cert petition. I read the cert petition as raising a pretty specific question: When a traffic stop is over, can the government extend the stop for a dog sniff, and if so, for how long? The narrow cert grant posed a bit of a problem because the Supreme Court has said little about how long traffic stops can extend generally. Without a theory of how long stops can last generally, it may be hard to answer what to do with specific question of delays at the end of a stop. As a result, several of the Justices wanted a general test for how long traffic stops should extend.

This focus was a problem for Rodriguez’s counsel, as he was ready to argue the narrow question but seemed unprepared to address the broader issue. Justice Sotomayor did her best to help him out, at times giving what amounted to impromptu advocacy advice. (Page 11: “It’s a policy question. So answer it as a policy question.  Don’t tie it to the stop or not.  Tie it to something else.”) But unfortunately, there wasn’t much in the way of clarity during the petitioner’s argument.

Ginger Anders, representing the United States, advocated a standard of reasonableness that gave the government a reasonable extension of time for dog sniffs. Anders suggested that officers should have the discretion to time a dog sniff at the beginning or the end of a traffic stop; in effect, an officer shouldn’t be penalized for bringing the dogs over at the end rather than the beginning. But Justice Kagan zeroed in on the problem with that view, I think: Why let the officer extend the stop without cause? We wouldn’t let an officer extend a stop because he wanted to take a cigarette break. Once we recognize that — which Anders rightly did — why allow an officer to extend a stop to wait for the dogs? To Anders, the difference was that there is a law enforcement purpose in bringing over the dogs even if there is no cause for doing so. The answer returned to one of the core questions the Justices had: If we’re going to say that the length of a traffic stop is reasonable based on some sort of core mission of the stop, how do we define the “core mission” of the stop?

Rodriguez raises several tricky issues, but I’ll just focus here on one: I think the core mission of a traffic stop is actually pretty easy to define. By way of background, it helps to distinguish two conceptually distinct kinds of traffic stops. The first and most common kind is a stop to enforce the traffic code. This kind of stop requires probable cause of a civil traffic violation. See Whren v. United States (1996). The second kind is a Terry v. Ohio stop based on reasonable suspicion of criminal activity. If a suspect happens to be in a car when he is spotted, the officer can stop the car to investigate the crime under Terry just as the officer would be able to if the suspect were on foot. See, e.g., Navarette v. California (2014). Some situations can involve both rationales, to be sure. For example, a drunk driving stop might be made under the criminal law Terry rationale (as in Navarette) or under the unsafe driving traffic-code rationale. But for the most part the two kinds of stops are distinct.

Rodriguez concerns the first kind of stop, a stop for a civil traffic violation such a having a broken tail light. I think such stops have a clear mission: public safety. Unsafe driving causes a great number of fatalities and injuries every year. We allow stops of cars for non-criminal traffic violations out of a judgment that such stops are reasonable to advance the public interest in safe driving. See Delaware v. Prouse, 440 U.S. 648 (1979). Traffic codes are all about safety. Cars need to be operating in a safe and proper manner (all lights working, all safety equipment, etc.) and to be driven in a safe manner (no speeding, proper signaling, etc.) Officers can make stops for civil traffic infractions — even when there is no hint of any criminal activity, unlike the case of a Terry stop — to advance those safety-related interests. See Prouse at 658 (“[T]he States have a vital interest in ensuring that only those qualified to do so are permitted to operate motor vehicles, that these vehicles are fit for safe operation, and hence that licensing, registration, and vehicle inspection requirements are being observed.”).

Accepting that rationale, we might say that the general standard for the proper length of a civil-traffic-violation-based traffic stop should be something like the time it takes a diligent officer to evaluate and address any safety concerns. The officer can conduct a visual inspection of the car to make sure it is operating properly. He can ask questions of the driver to ensure the driver isn’t impaired. He can run a license and registration check, as consulting the relevant state records provides an additional means of assessing the safety of the car (did it pass its most recent safety inspection?) and the driver (did he pass a driver’s test and not have any suspensions of his license?). The officer can take steps to protect his own safety, too, given the dangers traffic stops can pose to officers. See, e.g., Pennsylvania v. Mimms, 434 U.S. 106 (1977) (officer can order driver out of the car for officer safety reasons). These steps are all about safety, and we give officers the time to take these safety-related steps.

With this “core mission” defined, we can see that some other things that might happen during a stop, such as asking questions to try to generate consent to a search, or bringing out the drug sniffing dogs, are outside that core mission. Under Caballes, the Court allows such steps to occur so long as they don’t extend the length of the stop. And under Whren, the Court allows such steps even if they’re the real reason the officer made the stop. But those steps are nonetheless outside the core mission of the stop.

The government has a strong interest in investigating criminal activity, to be sure. But that’s not what civil-traffic-code stops are about. That criminal law interest is instead recognized by the alternative Terry rationale that allows stops when there is no traffic violation. The catch is that the Terry rationale requires a factual predicate for the stop, specific and articulable facts amounting to reasonable suspicion of a crime occurring, before the stop can occur on that basis.