Exclusionary Rule

Thus far we have concentrated on the exclusion of evidence obtained in violation of the Fourth Amendment. Sometimes, however, the police obtain evidence in violation of other constitutional provisions. For example, the Fifth Amendment privilege against self-incrimination can be overcome by a grant of official immunity. When a witness testifies before a grand jury or a legislative committee under an immunity order, the subsequent testimony may not be used at a subsequent criminal prosecution of the witness. Nor can the government use other evidence derived from the immunized testimony. The burden is on the government to prove that the additional evidence was obtained independently of the compelled testimony. If, at a subsequent trial, the previously immunized witness takes the stand and testifies inconsistently with the prior immunized testimony, the immunized testimony may not be admitted even for impeachment.

By contrast, although the famous warnings required by Miranda v. Arizona are premised on the Fifth Amendment privilege against self-incrimination, the Miranda exclusionary rule operates more like the Fourth than the Fifth Amendment exclusionary rule. Statements obtained in violation of Miranda v. Arizona are admissible to impeach, and other evidence derived from such statements is often admitted when the causal connection between the violation and the discovery of the evidence is attenuated. Although the Supreme Court recently reaffirmed the constitutional basis of the Miranda rules, the Court stopped short of equating Miranda violations with compelled testimony.

Before Miranda, the Supreme Court had established a due process test excluding confessions obtained by brutal or coercive police methods. The due process test remains as a supplement to Miranda. Because coerced confessions are thought to be both less reliable, and more offensive, than admissions obtained in violation of Miranda, a stricter exclusionary rule applies to coerced confessions. When a confession is actually coerced by brutality or other extreme forms of police pressure, the confession is not admissible even if the defendant at trial testifies inconsistently with the coerced admission.

The exclusion of eyewitness identification evidence obtained in violation of the Sixth Amendment right to counsel, or by unfair suggestiveness in violation of due process, differs from both the Fourth and Fifth Amendment context. Evidence of an unconstitutional pretrial lineup or photo identification procedure must be suppressed, but the witness will ordinarily be allowed to testify at the trial that she recognizes the defendant as the offender. The theory is that the witness's memory of the crime is independent of the pretrial lineup. Although highly doubtful in light of modern psychological research on identification, courts frequently allow the in-court identification, provided that the witness testifies that current memory is independent of the prior, tainted lineup or photo array. In this situation defense counsel sometimes introduces proof of the prior suggestive lineup (which counsel worked hard to have suppressed in the first place) as a necessary means to discredit the in-court identification.

Whether the exclusionary rule is an appropriate remedy for violations of the equal protection clause is an open question. If the police have probable cause to search or arrest a suspect, but the suspect can prove that the police were motivated by racial animus, there is a violation of the equal protection clause but not a violation of the Fourth Amendment. Some lower courts have considered whether such a suspect may suppress the fruits of the equal protection violation or if a damage action provides the exclusive remedy. It seems likely that the issue eventually will present itself to the Supreme Court.