In the case of Illinois v. Lloyd Perkins, 1989, the U.S. Supreme Court ruled on whether a recorded conversation could be used as evidence in court if one party was unaware they were being recorded. The defendant, Lloyd Perkins, had been arrested for murder and while in jail he confessed to his cellmate who was an undercover police officer wearing a wire. This confession was then used against him during trial leading to his conviction. However, Perkins appealed this decision arguing that his Fifth Amendment rights (protection against self-incrimination) had been violated because he did not know he was speaking with law enforcement when confessing to the crime. The Supreme Court disagreed with Perkins' argument and upheld his conviction stating that there is no constitutional right protecting individuals from unknowingly speaking with undercover officers or informants about their crimes without first receiving Miranda warnings (the requirement for police to inform suspects of their legal rights). The court reasoned that since there wasn't any coercion involved and it happened outside formal custodial interrogation setting where pressures might subvert individual's free will; hence it didn't violate Fifth Amendment protection.

The dissenting opinion in the case of Illinois v. Lloyd Perkins argued that the majority's decision to allow evidence obtained through a police officer posing as a fellow inmate was an overreach and violated Perkins' Fifth Amendment rights against self-incrimination. The dissenters believed that this ruling expanded law enforcement's ability to trick suspects into confessing without informing them of their Miranda rights, which they saw as fundamentally unfair and contrary to established legal principles. They also expressed concern about potential abuses of power by law enforcement under such a rule, including possible coercion or manipulation of vulnerable individuals in custody. Overall, they felt that confessions should be voluntary and informed for them to be admissible in court.