Consent is a very important law enforcement tool for avoiding the requirements of the Fourth Amendment. By obtaining consent, the police may conduct a search without the requisite justification (probable cause) and without the necessity for a warrant. In consenting, an individual, or in some instances a third party for an individual, is waiving the protections afforded by the Fourth Amendment. Therefore, the terms consent and waiver are used interchangeably here.
The Court, in its desire to aid the needs of law enforcement, has liberally interpreted the consent doctrine and generally finds consent, thereby avoiding the requirements of the Fourth Amendment. This approach implies a relaxing of Fourth Amendment requirements by allowing the police to obtain evidence without complying with the Fourth Amendment.
Shortly after the Mapp v. Ohio (1961) decision, the Court indicated that it viewed the Fourth Amendment as a kind of second-class protection. An example of this can be found in Linkletter v. Walker (1965), in which the Court refused to apply the full retroactive effect to Mapp that it had applied to decisions involving coerced confessions and right to counsel. Linkletter limited the retroactive effect to only those convictions occurring after Mapp. Before Linkletter, the Court applied its decisions to all cases still pending even if the case was decided before the constitutional ruling. The justification given for treating Fourth Amendment protected rights differently than Sixth Amendment (e.g., right to counsel) and Fifth Amendment (e.g., coerced confessions) protected rights was that the Fourth Amendment had nothing to do with the integrity of the fact-finding process. In other words, evidence obtained as a result of a Fourth Amendment violation will be useful or truthful evidence, thus contributing to the fact-finding process. However, evidence obtained as a result of a coerced confession will often be unreliable and thus will not contribute to the fact-finding process.