In the case of Maine v. Moulton, the U.S. Supreme Court ruled in 1985 that a defendant's Sixth Amendment right to counsel was violated when police arranged for a co-defendant to wear a wire during their meeting, without informing him or his counsel about it. The court held that once formal proceedings have begun against an individual, he has the right to legal representation when dealing with authorities and any attempt by law enforcement officials to elicit information from him outside of his attorney’s presence is considered as violating this constitutional protection. This decision reinforced the importance of ensuring defendants are aware they are being recorded and have access to legal advice before engaging in discussions which could potentially incriminate them.

In the dissenting opinion for Maine v. Moulton, Justice Powell argued that the majority's decision to suppress evidence obtained during a conversation between defendant and an informant violated principles of fairness and effective law enforcement. He contended that there was no Sixth Amendment violation because Moulton had not been formally charged with conspiracy at the time of his discussion with Colson, thus he did not have right to counsel for this charge yet. Furthermore, Powell believed that even if there were a violation, suppression of all statements made by Moulton about past crimes would be excessive; only those directly related to formal charges should be excluded from trial. The justice also expressed concern over potential negative impacts on police investigations due to limitations placed on use of informants in gathering information about ongoing or future criminal activities.