Law enforcement officers can violate the Fourth Amendment, and thereby open themselves up to liability under 42 U.S.C. section 1983 both by performance of an improper arrest and by something called “malicious prosecution.” But what’s the difference, and does this have anything to do with the actions of prosecutors, or is it just about police?
The more familiar idea, to most folks, is the bad arrest. A police officer or sheriff’s deputy stops and detains somebody, potentially escalating into a formal “arrest,” without a concrete basis to suspect that they’ve committed a crime. Under a straightforward application of the text of the Fourth Amendment, that’s an unreasonable seizure.
The idea of “malicious prosecution” is related, but it’s a little more complicated, in part because the idea of “malicious prosecution” is not actually found anywhere in the Fourth Amendment and is instead drawn from state common law. Malicious prosecution occurs based on “the wrongful initiation of charges without probable cause.” Thompson v. Clark, 596 U.S. 36, 43 (2022). Proof of “malicious prosecution” also generally requires showing a malicious motive for instituting the charges and termination of the case via acquittal or discharge. Id. at 44. Some caselaw interpreting California law also suggests a requirement of showing that the defendant prosecuted the plaintiff for the purpose of denying equal protection or another specific constitutional right. See Mills v. City of Covina, 921 F.3d 1161, 1169 (9th Cir. 2019).
Police officers take actions that “initiate charges,” so they can commit “malicious prosecution” even though officers are not themselves prosecutors. Chiaverini et al. v. City of Napoleon, Ohio, 144 S.Ct. 1745 (2024). Other state actors, such as a coroner or an investigator, can also commit malicious prosecution in some circumstances. Galbraith v. County of Santa Clara, 307 F.3d 1119, 1126 (9th Cir. 2002). Actual prosecutors on the other hand, are typically likely to rely on police reports that allege that crimes have occurred, and so are less likely to engage in “malicious prosecution” than law enforcement officers, unless they completely disregard what is suggested by the language of the police reports. Prosecutors also have a much broader range of immunities for their actions than do law enforcement officers, though police have various immunities as well.
Another interesting distinction between a “bad arrest” cause of action and a “malicious prosecution” cause of action is that they may “accrue” at very different times for purposes of determining when the statute of limitations begins to run. Most 1983 claims are subject to a 2-year statute of limitations (at least in California), but the time at which the claim accrues (starting the clock running) is governed by federal law. In a malicious prosecution case, the cause of action does not accrue until the criminal cause of action is terminated favorably to the plaintiff/defendant. McDonough v. Smith, 139 S. Ct. 2149, 2154-55, 204 L. Ed. 2d 506 (2019). Consequently, a malicious prosecution theory may be a way to pursue legal action against the individuals who caused charges to get filed in the first place (if the other elements of malicious prosecution appear satisfied) in a situation where a straightforward theory of a bad arrest would be barred by the passage of time for a person who has burned up years fighting the criminal case to a successful resolution.