In Utah v. Strieff,1Utah v. Strieff, 136 S. Ct. 2056 (2016). the Supreme Court declined to suppress evidence that the police had obtained as the result of an unlawful investigatory stop.2Id. at 2064. The Court reasoned that “the officer’s discovery of the arrest warrant,” which had intervened between the unlawful stop and the resulting search incident to arrest, had “attenuated the connection between the unlawful stop and the evidence seized incident to arrest,” thus making the evidence admissible.3Id. at 2059. In dissent, however, Justice Kagan challenged the Court’s conclusion that the officer’s discovery of the warrant had “br[oken] the causal chain.”4Id. at 2072 (Kagan, J., dissenting). The officer’s discovery of the warrant, she argued, far from being the kind of intervening circumstance that is sufficient to break the causal chain, was itself an “effect,” a “consequence,” of the unlawful stop.5Id. at 2073. “[R]ather than breaking the causal chain,” she said, “predictable effects (e.g., X leads naturally to Y leads naturally to Z) are its very links.”6 Id.; cf. Strieff, 136 S. Ct. at 2066 (Sotomayor, J., dissenting) (“The warrant check … was not an ‘intervening circumstance’ separating the stop from the search for drugs. It was part and parcel of the officer’s illegal ‘expedition for evidence in the hope that something might turn up.”’); Michael S. Moore, Causation and Responsibility 236 (2009) (“If [the intervening event is a product of the defendant’s act], then the event is merely part of the mechanism or means by which defendant’s act caused the harm …”).
Justice Kagan’s intuition–that the weight assigned to an intervening cause ought to depend in part on whether it was itself an “effect” of the actor’s wrongdoing–is not unique to her. Courts and scholars long have distinguished dependent intervening causes from independent intervening causes.7See Segura v. United States, 468 U.S. 796, 815 (1984) ( “[E]vidence will not be excluded as ‘fruit’ unless the illegality is at least the ‘but for’ cause of the discovery of the evidence.”); United States v. Smith, 155 F.3d 1051, 1060 (9th Cir. 1998) (describing attenuation analysis in the law of search and seizure as “akin to a proximate causation analysis.”); see generally Eric A. Johnson, Causal Relevance in the Law of Search and Seizure, 88 B.U. L. REV. 113, 115-16 (2008) (describing the operation of the twofold causation requirement in the law of search and seizure). Words Words Words Words Words Words Words Words Words Citation.