In the case of Weatherford v. Bursey (1976), the United States Supreme Court ruled that a government informant's presence at a meeting between an accused person and his lawyer did not automatically violate the Sixth Amendment right to counsel, unless it could be proven that confidential information was disclosed or used against him in court. The case involved Weatherford, an undercover agent who had infiltrated a group planning anti-war protests during President Nixon’s inauguration. He was arrested with Bursey for burning down draft board records but didn't reveal his identity as an agent even when they both consulted their defense attorney together. Later, he testified against Bursey without using any information from those meetings. The court held that while intrusion into attorney-client privilege is generally unacceptable, there must be demonstrated prejudice to warrant reversal of conviction.

In the case of Weatherford v. Bursey, Justice Brennan dissented from the majority opinion. He argued that any intrusion by a government agent into attorney-client confidentiality should be considered as prejudicial per se and thus automatically trigger reversal of conviction unless the government can prove beyond reasonable doubt that no prejudice resulted from such intrusion. According to him, this approach would better serve to deter future intrusions and protect Sixth Amendment rights than requiring defendants to demonstrate specific prejudice in each case. Furthermore, he criticized the majority for failing to recognize how even seemingly innocuous information could provide prosecutors with strategic advantages over defense counsel if improperly obtained through infiltration of attorney-client meetings.