State v. Engel: Minnesota Adopts a Four-Factor Test for Suppressing Evidence of a New Crime After an Unconstitutional Stop

What Happened in State v. Engel?

Shortly after midnight, a Thief River Falls officer tried to stop Engel's van because he did not see a rear license plate and could not read a sign in the rear window well enough to tell whether it was a temporary registration tag. It was, in fact, a valid Wisconsin temporary registration. Rather than stop, Engel turned on his hazard lights and continued driving for several miles, ignoring the officer's lights, siren, and repeated commands to pull over, before finally stopping. He was charged with felony fleeing a peace officer in a motor vehicle under Minn. Stat. § 609.487, subd. 3.

Engel moved to suppress the evidence of his flight, arguing the stop was an unlawful seizure and his flight resulted from that violation. The district court denied the motion; a jury convicted him; and the Court of Appeals affirmed. Every court agreed the stop itself was unlawful — an officer's inability to read a displayed temporary tag is not a reasonable, articulable suspicion of criminal activity. The question the Supreme Court took up was narrower: given an unconstitutional stop, must the evidence of the new crime committed in response be suppressed?

The Legal Problem the Court Resolved

Minnesota law had not been entirely clear on how to handle evidence of a new crime committed in response to an unconstitutional stop or search. The State argued for a near-bright-line rule — that evidence of a new crime is not suppressed unless police deliberately provoked it or exploited the illegality. Engel argued that courts should instead use the established four-factor attenuation test that Minnesota applies to other "fruit of the poisonous tree" questions.

The Supreme Court sided with the framework Engel proposed. It held that the fruit-of-the-poisonous-tree doctrine applies even when the evidence is of a new crime, and that courts must use the four-factor attenuation test from State v. Warndahl to decide whether that evidence is suppressed. The Court declined to read its earlier decisions in State v. Combs and City of St. Louis Park v. Berg as having adopted a separate, categorical "new crime" rule.

The Four-Factor Attenuation Test

Under Engel, a court deciding whether to suppress evidence of a new crime weighs four factors, with no single factor controlling:

• The purpose and flagrancy of the misconduct — described as especially important, because the exclusionary rule exists to deter police misconduct. Did the officer exploit the violation or provoke the new crime, and was the conduct particularly flagrant?
• The presence of intervening circumstances — did something, including the person's own free act, break the causal chain between the violation and the evidence?
• Whether the evidence likely would have been obtained anyway — absent the illegality.
• Temporal proximity — how much time passed between the violation and the evidence. This is often the least decisive factor.

How the Court Applied the Test to Engel

The Court balanced the factors and concluded the flight evidence was not suppressed. On purpose and flagrancy, it found the officer did not stop or pursue Engel to provoke flight or exploit the violation, and the conduct was not particularly flagrant — the officer believed the van was unregistered and was unfamiliar with Wisconsin's requirements. On intervening circumstances, the Court characterized Engel's miles-long flight, with multiple evasive maneuvers and refusals to stop, as an independent act of free will that purged the taint of the unlawful stop. Two factors — whether the evidence would have been obtained anyway and temporal proximity — favored suppression, since Engel would not have fled but for the stop and the flight followed immediately. On balance, though, the Court held the evidence was sufficiently attenuated and affirmed the conviction.

The Dissent

Justice Thissen dissented. In his view, the attenuation test fits poorly where the very evidence at issue is conduct made criminal because it was a direct response to the unconstitutional seizure — there, the causal connection is immediate and there is no real "gap" to analyze. He would ask instead whether a reasonable person would conclude that the unconstitutional seizure would have provoked the criminal response — that is, whether the person's reaction was common, predictable, unsurprising, and foreseeable. Because neither lower court had analyzed the case that way, he would have remanded. This framing is likely to feature in future suppression arguments.

Why This Matters

Two constitutional protections run through this case: the guarantee against unreasonable seizures under Article I, Section 10 of the Minnesota Constitution, and the exclusionary rule that remedies violations of it. Engel does not weaken the first — the stop was still unconstitutional. What it settles is the remedy question for a recurring scenario, and it does so with a fact-intensive test rather than a categorical rule. For anyone whose case involves a stop or search that may have been unlawful, followed by a separate charge arising from the response, the specific facts — the officer's purpose, the flagrancy of the conduct, and what happened in between — now drive whether that later evidence can be challenged.