In Trammel v. United States, the Supreme Court reevaluated the marital privilege rule that allowed defendants to prevent their spouses from testifying against them in court. The case involved Robert Trammel who was convicted for importing heroin into the U.S., based partly on his wife's testimony. He appealed, arguing this violated his rights under common law spousal privilege. However, the Supreme Court upheld his conviction and modified the existing rule of spousal disqualification. It ruled that while a witness-spouse alone has a privilege to refuse to testify adversely during trial; such right does not extend to allow one spouse to prevent adverse testimony by another spouse who is willing to testify voluntarily against him or her.

In the dissenting opinion for Trammel v. United States, Justice Stewart argued that the majority's decision to allow a spouse to testify against their partner in court was an infringement on marital privacy rights. He believed that this ruling would lead to potential harm and discord within marriages, as it could encourage spouses to betray each other’s trust under legal pressure. Furthermore, he contended that such testimonies might not always be reliable due to emotional entanglements between partners. The justice also pointed out that there were already existing exceptions where spousal privilege did not apply (e.g., cases of domestic violence), making further erosion unnecessary and potentially harmful.