On April 21, 2015, the Supreme Court of the United States released an important ruling in Rodriguez v. United States, 575 U.S. _ (2015) holding that the Fourth Amendment does not allow the police to extend the duration of a traffic stop without reasonable suspicion for reasons unrelated to vehicle and driver safety – even for a de minimis length of time. The court had granted certiorari to resolve a division among lower courts whether police routinely may extend an otherwise completed traffic stop, absent reasonable suspicion, in order to conduct a dog sniff.

In the 6-3 majority opinion, Justice Ruth Ginsburg began the analysis by addressing the permitted constitutional “mission” of a traffic stop which is to ensure that vehicles on the road are operated safely and responsibly. This principle allows the police to inquire into the traffic violation that justified the stop and to make safety related checks. Justice Ginsburg stated the following, slip op., at pp. 5-6:

“A seizure for a traffic violation justifies a police investigation of that violation. ‘[A] relatively brief encounter,’ a routine traffic stop is ‘more analogous to a so-called Terry stop…than to a formal arrest.’ Knowles v. Iowa, 525 U.S. 113, 117 (1998) (quoting Berkemer v. McCarty, 468 U.S. 420, 439 (1984), in turn citing Terry v. Ohio, 392 U.S. 1 (1968). See also Arizona v. Johnson, 555 U.S. 323, 330 (2009). Like a Terry stop, the tolerable duration of police inquiries in the traffic-stop context is determined by the seizure’s “mission” – to address the traffic violation that warranted the stop, Caballes, 543 U.S., at 407, and attend to related safety concerns, infra, at 6-7. See also United States v. Sharpe, 470 U.S. 675, 685 (1985); Florida v. Royer, 460 U.S. 491, 500 (1983) (plurality opinion) (‘The scope of the detention must be carefully tailored to its underlying justification.’). Because addressing the infraction is the purpose of the stop, it may ‘last no longer than is necessary to effectuate th[at] purpose.’ Ibid. See also Caballes, 543 U.S., at 407. Authroity for the seizure thus ends when tasks tied to the traffic infraction are – or reasonably should have been – completed. See Sharpe, 470 U.S., at 686 (in determining the reasonable duration of a stop, ‘it [is] appropriate to examine whether the police diligently pursued [the] investigation’)…

Beyond determining whether to issue a traffic ticket, an officer’s mission includes ‘ordinary inquiries incident to [the traffic] stop.’ Caballes, 543 U.S., at 408. Typically such inquiries involve checking the driver’s licence, determining whether there are outstanding warrants against the driver, and inspecting the automobile’s registration and proof of insurance. See Delaware v. Prouse, 440 U.S. 648, 658-660 (1979). See also 4 W. LaFave, Search and Seizure s. 9.3(c), pp. 507-517 (5th ed. 2012). These checks serve the same objective as enforcement of the traffic code: ensuring that vehicles on the road are operated safely and responsibly. See Prouse, 440 U.S., at 658-659; LaFave, Search and Seizure s. 9.3(c), at 516 (‘A warrant check makes it possible to determine whether the apparent traffic violator is wanted for one or more previous traffic offences.’).”

Having defined the law enforcement mission of a traffic stop, Justice Ginsburg concluded that the use of a sniffer dog fell outside the mission and cannot support delay in the absence of reasonable suspicion, slip. op., at p. 6-7:

“A dog sniff, by contrast, is a measure aimed at ‘detect[ing] evidence of ordinary criminal wrongdoing.’ Indianapolis v. Edmond, 531 U.S.1, _-_ (2013) (slip op., at 7-8). Candidly, the Government acknowledged at oral argument that a dog sniff, unlike the routine measures just mentioned, is not an ordinary incident of a traffic stop. See Tr. of Oral Arg. 33. Lacking the same close connection to roadway safety as the ordinary inquiries, a dog sniff is not fairly characterized as part of the officer’s traffic mission.”

The question then arose: Is there a valid reason to allow a de minimis extension of a traffic stop for reasons outside the mission of the stop? The majority concluded – no. The permissible length of a traffic stop is defined by how long it takes to diligently complete the steps that are the reason for the stop: (a) the inquiry into the violation; and, (b) safety related checks. In this context, Justice Ginsburg specifically stated at, slip. op., pp. 7-8, that an on-scene investigation into other crimes “detours” from the mission. So too do officer safety precautions taken in order to facilitate such detours: “Highway and officer safety are interests different in kind from the Government’s endeavour to detect crime in general or drug trafficking in particular.”

The Government argued that the test should be the overall reasonableness of the duration of the stop. Justice Ginsburg summarized the argument, slip. op., at p. 8: “The Government argues that an officer may ‘incremental[ly]’ prolong a stop to conduct a dog sniff so long as the officer is reasonably diligent in pursuing the traffic-related purpose of the stop, and the overall duration of the stop remains reasonable in relation to the duration of other traffic stops involving similar circumstances.” She then rejected the overall reasonableness argument, slip. op., at p. 8:

“The Government’s argument, in effect, is that by completing all traffic-related tasks expeditiously, an officer can earn bonus time to pursue an unrelated criminal investigation. See also post, at 2-5 (THOMAS, J., dissenting) (embracing the Government’s argument). The reasonableness of a seizure, however, depends on what the police in fact do. See Knowles, 525 U.S., at 115-117. In this regard, the Government acknowledges that ‘an officer always has to be reasonably diligent.’ Tr. of Oral Arg. 49. How could diligence be gauged other than by noting what the officer actually did and how he did it? If an officer can complete traffic-based inquiries expeditiously, then that is the amount of ‘time reasonably required to complete [the stop’s] mission.’ Caballes, 543 U.S., at 407. As we said in Caballes and reiterate today, a traffic stop ‘prolonged beyond’ that point is ‘unlawful.’ Ibid. The critical question, then, is not whether the dog sniff occurs before or after the officer issue a ticket, as JUSTICE ALITO supposes, post, at 2-4, but whether conducting the sniff ‘prolongs’ – i.e., adds time to – ‘the stop,’ supra, at 6.”

In an article titled Police can’t delay traffic stops to investigate crimes absent suspicion, Supreme Court rules published in The Washington Post edition of April 21, 2015, Professor Orin Kerr of the George Washington University Law School argued that Rodriguez is correctly decided: “I’m particularly pleased that the Court adopted the safety-based rationale for traffic stops,” he wrote. “…I think that is exactly right, and there hasn’t been much authority on this. For authority, the Court mostly relies on dicta in Prouse and Wayne LaFave’s oft-cited treatise. In the grand scheme of things, that’s relatively slim doctrinal pickings. But I think the Court was quite right on this, and that it’s a conceptually important step.”

I agree with Professor Kerr. The most important sentence in the majority opinion for Fourth Amendment jurisprudence is this one at, slip. op, p. 5: “Authority for the seizure thus ends when tasks tied to the traffic infraction are – or reasonably should have been – completed.” As Professor Kerr went on to say: “Unpacking that, there are two limits on the duration of a traffic stop. First, the stop has to end when the safety related tasks are done (absent reasonable suspicion that turns the traffic stop into a Terry stop). Second, the stop has to end when the safety-related tasks should have been done (again, absent reasonable suspicion that turns the traffic stop into a Terry stop). Either limit is sufficient.”

There are two kinds of Rodriguez claims that can be made by defence counsel. Professor Kerr described them as: “First, they can argue that the tasks actually had been completed and the stop was over, not allowing any further delay. Second, they can argue that the officer was taking his sweet time and delayed the stop, ending his constitutional authority for the stop even though the safety-related checks were not complete. (The latter kind of claim is probably more important, even though the former is the focus of Rodriguez.)”

The Rodriguez rule may be more important for its impact on police asking questions than the use of sniffer dogs. The police ask questions outside the scope of traffic stops all the time. That raises the issue of remedy. Professor Kerr put it this way: “Is the remedy for the second kind of Rodriguez violation – that is, a claim that a stop went on for too long because the officer was dilly-dallying – suppression of evidence from the entire stop, or only suppression of what occurred after the stop should have ended? I would think the latter. If that’s right, the officer’s incentive is to ask incriminating questions, request consent, etc., early on in the stop to avoid getting close to the line. At the end of the stop, when the officer is handing back the driver’s licence and maybe writing a ticket or a warning, the officer still can ask questions unrelated to the stop. But at that point the officer is going to be vulnerable to a Rodriguez challenge that the officer improperly delayed the stop to ask unrelated questions.”

What, then, does Rodriguez have to say about Fourth Amendment law? Proponents of the right to privacy, such as myself, may argue that Rodriguez does not go far enough. But, and this is important, the Supreme Court in Caballes said that time is the key variable. As Justice Ginsburg observed, slip. op., at p. 8: “As we said in Caballes and reiterate today, a traffic stop ‘prolonged beyond’ [the amount of time reasonably required to complete the stop’s mission] is ‘unlawful’.” As Professor Kerr suggested, given the parameters of the arguments in play, “Rodriguez ends up imposing a limit on the variable of time.” (See also: Kerr. How long can a traffic stop last? A few thoughts on the Rodriguez argument. The Washington Post. January 23, 2015)