In the Massiah v. United States case of 1963, the U.S Supreme Court ruled that a defendant's Sixth Amendment right to counsel was violated when federal agents used an informant to elicit incriminating statements from the defendant after he had been indicted and retained a lawyer. The case involved Winston Massiah, who was charged with narcotics offenses. While out on bail, he made self-incriminating statements during a conversation with his co-defendant in absence of his attorney; unbeknownst to him, this conversation was being monitored by government officials through radio transmitter installed in the co-defendant’s car without Massiah's knowledge or consent. These statements were later used as evidence against him at trial leading to conviction which prompted appeal up to Supreme Court level arguing violation of constitutional rights under Sixth Amendment. The court agreed ruling 7-2 in favor of Massiah stating that once formal charges are filed and legal representation obtained any attempt by authorities for deliberate elicitation is unconstitutional unless waiver has been given knowingly and intelligently.

In the dissenting opinion for Massiah v. United States, Justice White argued that the majority's ruling was too broad and could potentially hinder law enforcement efforts to investigate crimes effectively. He contended that there should be a distinction between interrogations intended to elicit incriminating responses and casual conversations where such information might inadvertently come up. According to him, only in cases of deliberate elicitation should constitutional protections apply. Furthermore, he believed that if an accused person had legal representation or not at the time of questioning shouldn't determine whether their rights were violated because it would create unnecessary complications in determining when someone is truly "represented." Lastly, he expressed concern about how this decision could affect future investigations by limiting police officers' ability to gather evidence from willing informants who have access to suspects after indictment.