Bench & Bar of Minnesota is the official publication of the Minnesota State Bar Association.

Motor Vehicle Stops: A Four-Step Analysis Every Attorney Should Know

Whenever a motion to suppress challenges the legality of a motor vehicle stop, a four-step constitutional analysis is in order.  This starts by determining whether the facts of your case implicate the 4th Amendment to the United States Constitution.

Regardless whether the person before the court is a criminal defendant seeking suppression of evidence or a petitioner in civil Implied Consent proceedings, the legal argument they most commonly raise is to challenge the admissibility of evidence obtained by law enforcement as a result of a motor vehicle stop.

Whenever a motion to suppress challenges the legality of a motor vehicle stop, a four-step constitutional analysis is in order.  This starts by determining whether the facts of your case implicate the 4th Amendment to the United States Constitution.

1. Is The 4th Amendment Implicated?

Because stopping a motor vehicle or preventing a vehicle from moving constitutes a “seizure,” the 4th Amendment clearly applies to all motor vehicle stops.  The 4th Amendment prohibition against unreasonable searches and seizures requires that an investigative stop be supported by reasonable suspicion of misconduct.1  Under the 4th Amendment exclusionary rule, evidence obtained as a result of an unconstitutional seizure is not admissible in a court of law.2  However, the 4th Amendment and the exclusionary rule only apply when and if a person or motor vehicle is actually stopped by police.

Definition of “Stop” (Seizure):  In defining what constitutes a “stop,” courts have adopted an objective test.  A person or motor vehicle is considered to be stopped within the meaning of the 4th Amendment if, by means of “physical force” or a “show of authority,” a reasonable person would believe that he was not free to leave.3 Under the Minnesota Constitution, a “seizure” occurs at the point a peace officer orders a person to stop (verbally or by action),4 or does or says anything that would cause a reasonable person to believe he was not free to leave.5  Under the Minnesota rule, a seizure can occur even though the person does not immediately stop or otherwise submit to the officer’s show of authority.6

Stop v. Contact: The mere act of an officer approaching a person who is standing on a public street, or sitting in a car that is parked, and asking questions does not require a “reasonable suspicion.”  Such inoffensive contact between a citizen and the police is not considered to be a “seizure.”  In other words, a peace officer can approach, seek the cooperation of, and direct questions to anyone they want without having a reasonable suspicion, as long as they do not turn the contact into a “seizure” by ordering the person to stop or by doing or saying anything that would cause the person to believe that she was not free to leave.7

Assuming the facts of your case do implicate the 4th Amendment, then step two of the analysis is ascertaining the general rule.

2. What is the General Rule? 

A peace officer can stop and temporarily detain a motor vehicle whenever an officer has specific and articulable facts which, when taken together with reasonable inferences from those facts, reasonably warrant the intrusion.8  In other words, to make an investigatory stop, an officer must have a “reasonable suspicion” that a crime has been or is being committed.9 While the standard is less demanding than probable cause or a preponderance of the evidence,10 it nonetheless requires “at least a minimal level of objective justification.”11 The stop must not be based upon “mere whim, caprice, or idle curiosity.”12 The threshold question in every motor vehicle stop is whether, under the circumstances, the officer acted reasonably. In order to properly apply this general rule a further understanding of “reasonable suspicion” is necessary.

3. What is Reasonable Suspicion?  

“Reasonable suspicion” entails some minimal level of objective justification for making a stop.13  It is something more than instinct, unparticularized suspicion or “hunch,” but less than the level of suspicion required for probable cause.14 The threshold for finding an adequate factual basis for an investigative stop is “very low.”15  Although any traffic violation will justify a motor vehicle stop, an actual traffic violation need not occur.16  However, a peace officer cannot stop a motor vehicle without cause or reason, nor can the stop be based upon mere curiosity, suspicion, or assumption unsupported by facts.17  In order to determine if the stop was based on a “reasonable suspicion” the court must apply the proper legal standard.

4. The Totality of the Circumstances

In determining whether the stop was justified, the totality of the circumstances surrounding the stop must be taken into account.18  The process does not deal with “hard certainties,” but rather with probabilities.19  Furthermore, the evidence must be viewed from the vantage point of those versed in the field of law enforcement.  In other words, trained peace officers can make inferences and deductions that might elude untrained persons.20  For example:

a. Objective Determination: Ascertaining “specific and articulable facts” is an objective determination.  It doesn’t matter when or why a peace officer decides to stop a driver as long as sufficient objective facts justifying the stop exist at the time the stop occurs.21

b. Consideration of Past Criminal Conduct: A motor vehicle occupant’s past criminal behavior is a factor an officer may take into consideration in forming a reasonable suspicion justifying an investigative stop.22

c. Reasonable Mistakes Made by Peace Officers: An investigative stop is invalid where the stop is based on an officer’s mistaken interpretation of the law, whether or not the stop was made in good faith.23  However, the mistaken belief that the driver of a motor vehicle was a person whose driver’s license was suspended is sufficient to justify an investigative stop, even though the driver turns out to be somebody else.24  An investigative stop was valid where a peace officer stopped a car the officer reasonably believed was the one they had been following which had engaged in “questionable” driving activity.  The fact that police actually stopped the wrong car did not invalidate the stop.25

d. Innocent Conduct: The fact that the suspicion-arousing behavior eventually proves to be completely innocent will not invalidate the stop.  The relevant inquiry is not whether the conduct in question is innocent or guilty, but the degree of suspicion that attaches to particular types of noncriminal acts.”26

e. Insufficient Reasons to Stop Motor Vehicle: The mere fact that a person is in a high-crime area, is a stranger, or appears to be lost does not constitute a sufficient basis to justify an investigative stop.27 Slowing down at a yield sign at the end of a parking ramp does not constitute an “articulable ground” for an investigative stop.28  An investigative stop of an automobile after the vehicle swerved once, but stayed in its lane, was improper.29


The four-step constitutional analysis noted above should be applied whenever a Motion to Suppress challenges the legality of a motor vehicle stop. Because that four-step analysis will form the foundation for most judicial rulings, an attorney’s legal argument should thoroughly address each of those constitutional principles. Effectively arguing these principles within the context of the facts of the case will significantly increase the likelihood of success regardless of which side is being argued.

Judge Alan F. Pendleton has served as a judge of the 10th Judicial District since 1999. He is actively involved in attorney and judicial training programs, serves on the Supreme Court Judicial Faculty Development Team, and has offered instruction at several local universities and law schools as well as the National Institute of Trial Advocacy and the National Judicial College in Reno, NV.  He currently authors the “Minnesota Judicial Training Updates” which are distributed biweekly throughout the state.  He recently wrote a new publication titled “Minnesota Handbook on Motor Vehicles: Stops, Warrantless Searches, Seizures.


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