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The Fourth Amendment and K-9 Searches

Danny Clancy

By Danny Clancy

We’re all familiar with the saying “dog is man’s best friend,” and use this common colloquialism to describe the companionship offered by our furry friends. While this notion may hold true with our own pets, one may view the expression differently if confronted by a K-9 officer.

Picture this scenario: police pull you over for speeding and request your license and registration. Next, the officer proceeds to his vehicle seemingly to issue you a citation for the traffic violation. The officer returns to your car after a few moments and informs you that he has called for a K-9 to conduct an open-air search of your vehicle. Can the officer detain you, and wait for a K-9 to arrive to search? No, unless the officer has “reasonable suspicion” to believe that other criminal activity is occurring or has occurred.

The Supreme Court has held that a seizure justified only by a traffic violation becomes unlawful when prolonged beyond the time reasonably required to conduct the traffic stop. Rodriguez v. United States, 135 S. Ct. 1609 (2015). Typically, a traffic stop is concluded once the officer has issued the citation, and confirms no outstanding warrants exist. To continue a detention beyond this point there must be reasonable suspicion of criminal activity apart from the traffic violation.

To have reasonable suspicion, an officer must have specific, articulable facts that would lead him to reasonably conclude that a particular person actually is, has been, or soon will be engaged in criminal activity. These articulable facts only justify an investigative detention if they support more than a mere hunch or intuition of criminal activity. They must clearly show unusual activity, evidence connecting the detainee to the unusual activity, and evidence that the unusual activity relates to crime. Lastly, these facts “must be sufficiently distinguishable from that of innocent people under the same circumstances as to clearly, if not conclusively, set the suspect apart from them.” Wade v. State, 422 S.W.3d 661, 670 (Tex. Crim. App. 2013).

In determining what facts support reasonable suspicion, Texas courts have found that acting nervous and changing of the driver’s story alone are insufficient to justify a prolonged detention. While nervous and evasive behavior can be relevant, such behavior is not particularly probative in determining reasonable suspicion for a prolonged detention because most citizens with nothing to hide will nonetheless manifest an understandable nervousness in the presence of a police officer. Even further, “the more accusatory the questions that an officer asks, the more nervous a citizen legitimately becomes.” Id. at 671. Additionally, refusing to consent to a search of the vehicle cannot form any part of the basis for reasonable suspicion as consideration of such refusal would violate the Fourth Amendment. So other factors must be articulated by officers. These additional factors can include a prior criminal record or arrests for drug offenses, presence in a high-crime area late at night, or strong smells of drugs or other odors commonly used to hide the odor of drugs.

Lastly, the Supreme Court has issued an explicit warning to officers not to use traffic stops as simply a means to conduct “fishing expeditions.” Ohio v. Robinette, 519 U.S. 33, 41 (1996). Officers must evaluate the reason for and scope of the initial detention so that once the original purpose for the stop is completed, police may not further detain drivers solely in hopes of finding evidence of another crime.

It is clear that an officer cannot unreasonably prolong a traffic stop in order to conduct a dog sniff without the requisite reasonable suspicion, but this then begs the question, how long is too long? While there is no specific time limit for the reasonable length of a traffic stop, such a stop may not be used as a fishing expedition for evidence of an unrelated crime. Courts vary in what they deem to be a reasonable prolongation of a traffic stop based on the facts and circumstances of the individual case. If a dog arrives on the scene before the initial stop is complete or an officer establishes reasonable suspicion, courts will likely find the stop was not unreasonably prolonged. It is important to note though that courts have found dog sniffs that occur just 15 to 19 minutes into a stop have been deemed a violation of the Fourth Amendment when an officer cannot support his reasonable suspicion to detain with articulable facts.

In all, it is clear that an officer may not further detain a driver after the completing a traffic stop without sufficient reasonable suspicion that the driver has committed or is committing another crime. Dogs may in fact be man’s best friend, but in the event of a traffic stop, followed by a K-9 search, maybe not.

Daniel Clancy, a criminal defense attorney in North Texas, maintains a practice focused on federal criminal offenses, as well as felony and misdemeanor state offenses. A native Texan and a 1991 graduate from Mississippi College School of Law, Danny holds licenses in Texas and in both the Northern and Eastern Districts. Having been a county prosecutor and criminal district court judge, Mr. Clancy has seen the courtroom from every view possible and has tried or presided over hundreds of criminal cases. For more information, visit or call (214) 740-9955.