Source: http://www.wisconsinappeals.net/on-point-by-the-wisconsin-state-public-defender/arrest-probable-cause-predicated-on-mistake-of-law/
Timestamp: 2019-04-21 04:27:37+00:00

Document:
For Longcore: William E. Schmaal, SPD, Madison Appellate.
… The issue is, then, whether an officer has probable cause that a law has been broken when his interpretation of the law is incorrect. If the facts would support a violation only under a legal misinterpretation, no violation has occurred, and thus by definition there can be no probable cause that a violation has occurred. We conclude that when an officer relates the facts to a specific offense, it must indeed be an offense; a lawful stop cannot be predicated upon a mistake of law.
There is no reason to doubt that conclusion, with an important caveat: the police may be mistaken as to the fact of a violation, as opposed to mistaken as to the law. See,e.g. State v. Wimberly, FL App No. 5D07-3444, 7/21/08 (“A traffic stop based on an officer’s incorrect but reasonable assessment of the facts does not violate the Fourth Amendment. … If an officer makes traffic stop based on a mistake of fact, the court must determine whether the officer’s mistake of fact was reasonable. … The same would not be true with respect to an officer’s mistake of law.”); People v. Cole, Ill App No. 4-05-0672, 1/9/07 (“We agree with the majority of federal courts of appeal that a traffic stop based on a mistake of law is generally unconstitutional, even if the mistake is reasonable and made in good faith. … [T]raffic stops based on an officer’s objectively reasonable mistake of fact rarely violate the fourth amendment. … However, a police officer who mistakenly believes a violation occurred when the acts in question are not prohibited by law is not acting reasonably.”); U.S. v. McDonald , 453 F.3d 958 (7th Cir 2006) (“We agree with the majority of circuits to have considered the issue that a police officer’s mistake of law cannot support probable cause to conduct a stop.”); U.S. v. Tibbetts , 396 F.3d 1132 (10th Cir 2005) (stop may be based on reasonable mistake of fact, but mistake of law is impermissible); U.S. v. Cole , 5th Cir No. 05-50686, 3/30/06 (extending good-faith rule to traffic stop would violate holding of Whren v. U.S., 517 U.S. 806 (1996) that officer’s subjective beliefs irrelevant to question of whether police action objectively justifiable); U.S. v. Gross, 6th Cir No. 07-5971, 12/22/08 (fn 2: collecting federal cases).
But see, U.S. v. Delfin-Colina , 464 F.3d 392 (3rd Cir 2006) (mistake of law doesn’t render traffic stop per se unreasonable, and despite trooper’s misconstruction of applicable law stop upheld; however, the case certainly seems more like mistake-of-fact than law: “an objective review of the facts shows that an officer who correctly interpreted § 4524(c) and was in Trooper Wagner’s position would have possessed reasonable suspicion to believe that Delfin-Colina was in violation of § 4524(c)”); U.S. v. Rodriguez-Lopez , 8th Cir No. 05-3139, 4/24/06 (“the resolution of the case turns upon whether Detective Bandy’s belief that the statute was violated was objectively reasonable not whether it was in fact violated”; thus, even though defendant’s failure to signal may not have violated traffic law, officer’s belief that it was a violation wasn’t unreasonable); U.S. v. Washington , 8th Cir No. 06-1220, 8/1/06 (same; contrary authority recited, fn. 1). This could be a cert-worthy split of authority. Keep in mind, too, that the perception must at least be a reasonably mistaken fact,U.S. v. Chantasouxat, 342 F.3d 1271, 1281 (11th Cir. 2003) (“if an officer makes a traffic stop based on a mistake of fact, the only question is whether his mistake of fact was reasonable”).

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