Introduction

Suppressing Unlawfully Obtained Evidence

Introduction

An unconstitutional search or arrest can turn up evidence that is entirely trustworthy. The cocaine is cocaine and the pistol is a pistol, however the police came to find them. A finding that officers violated the Fourth Amendment therefore does not answer the question a trial judge faces next, which is whether the jury will hear the evidence. That question belongs to a separate remedy, the exclusionary rule, a device that makes evidence obtained in violation of a defendant's constitutional rights inadmissible at the defendant's trial.¹ The remedy is costly in a way that other exclusion rules are not. Suppressing a coerced confession or a suggestive lineup protects the reliability of the factfinding process, but suppressing the fruits of an illegal search usually removes reliable proof, and when the evidence is the clinching item the prosecution may collapse.² For that reason courts have given the remedy its own rules about when it applies, how far it reaches, and when it yields. This chapter teaches those rules and assumes the violation; whether a particular search or arrest was unconstitutional is the subject of neighboring readings. A breach of a police department's internal regulations does not trigger the rule on its own, because such regulations do not enlarge what the Constitution requires.³

The starting point is Mapp v. Ohio, which held that the exclusionary rule binds state courts through the Fourteenth Amendment's Due Process Clause, so that all evidence obtained by searches and seizures in violation of the Constitution is inadmissible in state court just as it is in federal court.⁴ After Mapp, suppression is the remedy in every American criminal court, and the Court described the rule as an essential part of the Fourth and Fourteenth Amendments that serves to deter police misconduct.⁵ Deterrence is the most prominent justification, but courts have also pointed to judicial integrity, meaning that judges should not become accomplices in disobeying the Constitution, and to public trust, meaning that the government should not profit from its own lawless behavior.⁶ Modern decisions lean on the deterrence rationale. In United States v. Leon the Court called the rule a judicially created remedy that safeguards Fourth Amendment rights generally through its deterrent effect, rather than a personal constitutional right of the party aggrieved, and it weighed the substantial social costs of exclusion against the marginal benefit.⁷ That cost-benefit framing explains why the rule has exceptions at all.

The chapter follows the order in which a suppression problem is actually worked. The first step is to identify the unlawful act, since exclusion presupposes a constitutional violation. The second is to trace what that act produced, because the rule reaches past the item the police seized directly to evidence derived from it. The third asks whether a doctrine saves the evidence despite the taint, and the fourth asks whether the modern deterrence calculus still calls for exclusion once good-faith reliance and the limits on suppressing for police negligence are taken into account. The final step is procedural, because the defendant must raise the claim by a pretrial motion to suppress. The next section begins with where the rule comes from and why courts enforce it.