Which police interrogation methods can make a confession inadmissible in court?

In the United States, police interrogation methods that violate a suspect's constitutional rights or fail to adhere to established procedural safeguards can render a confession inadmissible in court.

Constitutional and Procedural Grounds for Inadmissibility

• Coercion and Due Process: Confessions obtained through physical force, threats of violence, or mental torture are inadmissible as they violate due-process rights. Intense psychological pressure, such as exceptionally long periods of continuous interrogation, can also render a confession involuntary and inadmissible.12
• Miranda Violations: Under Miranda v. Arizona, police must inform suspects in custody of their Fifth Amendment right to remain silent and their right to an attorney before interrogation begins. Failure to provide these Miranda warnings generally results in the exclusion of the confession as evidence.134
• Unreasonable Delay: Historically, confessions obtained after an "unreasonable delay" in bringing a suspect before a judge for arraignment were excluded in federal courts. While this rule has been weakened, courts still scrutinize confessions secured during unusually long pre-arraignment detentions.1

It is a fundamental principle of justice that the state must respect the rights of the accused; therefore, evidence obtained through oppressive or unconstitutional means is suppressed to protect the integrity of the judicial system.12