In Whren v. United States, 517 U.S. 806 (1996), the US Supreme Court clarified that “[s]ubjective intentions play no role in ordinary, probable-cause Fourth Amendment analysis.” Id. at 813. “[A]s long as the circumstances, viewed objectively, justify [the police officer’s] action,” the officer’s subjective state of mind is irrelevant. Id. (quoting Scott v. United States, 436 U.S. 128, 136, 138 (1978)). The logic of Whren v. United States, is inherently two-sided: if an officer’s subjective motive or belief cannot invalidate an objectively justified traffic stop, then it cannot save an objectively unjustified one. In other words, Whren grants officers “broad leeway to conduct searches and seizures regardless of whether their subjective intent corresponds to the legal justification for their actions. But the flip side of that leeway is that the legal justification must be objectively grounded.” United States v. Miller, 146 F.3d 274, 279 (5th Cir. 1998) (footnote omitted). Where the actions the officer observes provide no basis for concluding that any law, as properly construed, has been violated, an officer’s subjective misunderstanding of the law cannot create the suspicion the Fourth Amendment requires.
The Eighth Circuit has found that an officer’s “subjective good faith belief about the content of the law is irrelevant,” United States v. Washington, 455 F.3d 824, 827 (8th Cir. 2006). According to the Eighth Circuit, “the constitutionality of [a] traffic stop … depends on whether [the officer’s] belief that a state law was violated was objectively reasonable.” Id.; accord United States v. Martin, 411 F.3d 998, 1001 (8th Cir. 2005).
Ordinary people are charged with knowledge of substantive criminal law, and if they make mistakes of law, they may not (absent special statutory exceptions) assert such mistakes as a defense to liability. This is so no matter how “objectively reasonable” a mistake may be. As has been said time and again, “ignorance of the law is no excuse.” Bryan v. United States, 524 U.S. 184, 196 (1998). Indeed, as Justice Holmes famously explained, “to admit the excuse at all would be to encourage ignorance where the law-maker has determined to make men know and obey.” Oliver Wendell Holmes, The Common Law 48 (1881). The expectation that the law is “definite and knowable” is no more tenable for police today than it is for the lay public.
It takes little reflection to see “the fundamental unfairness” of holding citizens to strict compliance with the law “while allowing those entrusted to enforce the law” to interpret and apply the law more flexibly. United States v. Chanthasouxat, 342 F.3d 1271, 1280 (11th Cir. 2003) (internal quotation marks omitted). “Reciprocal expectations of law-abidingness between government and its citizens can scarcely be expected to endure if one party – the government – need not uphold its end of the bargain.” Wayne A. Logan, Police Mistakes of Law, 61 Emory L.J. 69, 91 (2011) (footnotes omitted). Indeed, if anything, those charged with enforcing the law should be expected to have a better – not worse – understanding than the general public. Any rule that undermines this actuality, and that rewards police officers with more authority when they are ignorant of the law they are supposed to be enforcing, flouts our most basic constitutional values.