The Corrosive Effect of Inevitable Discovery on the Fourth Amendment

59 Pages Posted: 15 Mar 2022 Last revised: 6 Jun 2022

Date Written: February 15, 2022


The Supreme Court has only once, almost four decades ago, addressed the doctrine of inevitable discovery, when it established the exception in Nix v. Williams. Inevitable discovery encapsulates the notion of no harm, no foul—if law enforcement would have discovered unlawfully obtained evidence regardless of a constitutional violation, then the resulting evidence need not be excluded.

Nix laid out two simple dictates: the eponymous requirement of inevitability and a corresponding preponderance evidentiary burden. That is, the doctrine should only apply when the prosecution has proven by a preponderance of the evidence that law enforcement inevitably would have discovered the evidence without the violation. Such analysis requires counterfactual speculation, imagining a world but-for the unlawful police action, and so permits judges tremendous discretion. In the absence of further guidance by the Supreme Court, federal circuits have fashioned highly varying doctrinal tests to implement the doctrine.

This Article identifies some tests which constitute legitimate experimentation—permissible variation attempting to faithfully operationalize the dictates of Nix—but shows that other tests have devolved to the point of blatant manipulation—including some which prescribe a laxer “reasonable probability” standard, in defiance of the titular requirement of inevitability. Inevitable discovery is often combined with inventory searches, which permit suspicionless searching under the guise of bureaucratic process. Inventory searches apply automatically in numerous circumstances and consequently, under the laxer definitions of inevitability, evidence found in violation of the Fourth Amendment is almost always “inevitably discovered.” Likewise, “hypothetical search warrants” enormously expand the reach of inevitable discovery, admitting evidence when police fail to seek independent judicial approval before searching, on the theory that they could have and would have obtained proper judicial sign-off in a counterfactual world. The result of these doctrinal combinations is an unraveling of the substantive protections that the Court crafts in other criminal procedure domains: the doctrinal minutiae of exceptions such as search incident to arrest become meaningless when evidence found is routinely admitted through inevitable discovery.

For the Fourth Amendment to provide any substantial protection, this colossal loophole must be closed. We outline a range of potential reforms, identify which reforms must have highest priority, and provide a new framework by which inevitable discovery could be re-oriented to avoid the hollowing out of the Fourth Amendment’s protections.

Keywords: constitutional criminal procedure, inevitable discovery, exclusionary rule, Fourth Amendment, Roberts Court, Circuit split

Suggested Citation

Jacobi, Tonja and Louthen, Elliot, The Corrosive Effect of Inevitable Discovery on the Fourth Amendment (February 15, 2022). University of Pennsylvania Law Review, Vol. 171, 2023 Forthcoming, Northwestern Public Law Research Paper No. 22-19, Available at SSRN: or

Tonja Jacobi (Contact Author)

Emory University School of Law ( email )

1301 Clifton Road
Atlanta, GA 30322
United States

Elliot Louthen

Northwestern University, Pritzker School of Law ( email )

Evanston, IL 60208
United States

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