[1] It is one of several exceptions to the exclusionary rule, or the related fruit-of-the-poisonous tree doctrine, which prevent evidence collected in violation of a defendant's constitutional rights from being admitted in court.
[2][3] In that case, Williams, the defendant, challenged the admissibility of evidence about the location and condition of the victim's body, given that it had been obtained from him in violation of his Sixth Amendment right to counsel.
The inevitable discovery doctrine gives force to that other side of the balance by rendering evidence admissible when it would simply put police in the same position they would have been in had they exclusively used lawful means.
Given the inherently speculative nature of inevitable discovery, Justice Brennan would have demanded that the prosecution satisfy a clear and convincing standard before being allowed to use the evidence.
The Court also took Nix as an opportunity to resolve a point of contention with regard to the relevance of bad faith to applicability of the inevitable discovery doctrine.
In the lower court proceedings in Nix, the Eighth Circuit had adopted a version of the rule that would require the state to not only show that the evidence would inevitably have been discovered, but also that the police did not act in bad faith, i.e., with the intention of committing misconduct.
[14][15] For instance, the Eighth Circuit has required that "the government was actively pursuing a substantial, alternative line of investigation at the time of the constitutional violation" for the exception to apply.
"[18][19] In the Tenth Circuit case of United States v. Cunningham, the defendant objected that evidence obtained from his house indicating that he was guilty of counterfeit check-writing should be suppressed because the police had no warrant and his consent to the search was coerced.
[3] For instance, in United States v. Infante-Ruiz, the defendant sought to suppress evidence of a firearm that officers had found while searching a briefcase in the trunk of a rental car he was a passenger in, after arresting him on outstanding, unrelated narcotics charges.
[30] The independent source rule dates all the way back to the Supreme Court's 1920 case of Silverthorne Lumber Co. v. United States,[31] well before the adoption of the inevitable discovery doctrine.
But in Nix, the Court explicitly noted that the rationale underlying the independent source rule—balancing competing interests by putting police in the same, not a worse, position that they would have been in absent the illegality–applied with equal force to justify the inevitable discovery exception.
The Hawaii Supreme Court explained this choice of a higher standard of proof as a product of the fact that its state constitution provides greater protection for individual privacy than does the federal constitution; thus, the Hawaii Supreme Court wanted to ensure that "speculation regarding whether evidence obtained in violation of one's individual privacy would have been inevitably discovered be 'as close to correct as possible.
Many have argued that, despite the Court's assurances to the contrary in Nix, the inevitable discovery rule not only permits but encourages, law enforcement to engage in misconduct by, for example, creating an easy "I could have gotten a warrant" excuse for a warrantless search.
[12] Professor Robert Bloom critiques the Nix Court as having improperly minimized the "negative effect that the inevitable discovery exception would have on the deterrence rationale of the exclusionary rule"; he posited that the Supreme Court neglected the immense incentives the exception would create to conduct unconstitutional searches and seizures in the Fourth Amendment context because Nix itself is a Sixth Amendment case.
[40] These scholars have especially emphasized how the expansion of the inevitable discovery doctrine to primary evidence and the lack of an active pursuit rule in some circuits have rendered it a more dangerous threat to constitutional rights.
Mark Rasch has argued that the Supreme Court's ruling in Carpenter, requiring law enforcement to get a warrant to access cell-site location information (data about what cell towers a phone has pinged), has been rendered meaningless by a combination of the good-faith exception and the inevitable discovery doctrine.