In the 1980 case of Upjohn Co. v. United States, the U.S Supreme Court ruled in favor of attorney-client privilege extending to internal corporate investigations. The case arose when Upjohn Company conducted an internal investigation into alleged illegal payments made by company executives and managers to foreign officials. During this process, questionnaires were distributed among employees which were later subpoenaed by the Internal Revenue Service (IRS). The IRS argued that attorney-client privilege did not apply as it was not a direct communication between lawyer and client but rather with lower-level employees who do not constitute 'the client'. However, the court held that these communications were indeed protected under attorney-client privilege because they had been made for obtaining legal advice about potential liability stemming from those payments. This decision significantly broadened the scope of attorney-client privilege within corporations.

In the dissenting opinion for Upjohn Co. v. United States, Justice William Brennan disagreed with the majority's broad interpretation of attorney-client privilege in corporate settings. He argued that this expansive view could potentially shield corporations from legitimate investigations into their activities by protecting any communication between employees and company lawyers under the guise of legal advice. Instead, he proposed a narrower definition where only communications between top management and attorneys would be protected as privileged information to ensure accountability within corporations while still preserving necessary confidentiality in legal matters.