In the case of Smith v. Illinois, 1967, the United States Supreme Court ruled in favor of defendant Willie Edward Smith. The court found that his Sixth Amendment right to confront witnesses against him was violated during his trial for selling heroin. During cross-examination, the defense attorney asked for the name and address of an informant who had purchased drugs from Smith as part of a police operation but was denied by both prosecution and judge citing safety concerns for their witness. This denial limited Smith's ability to challenge credibility or potential bias on behalf of this key witness against him which led to his conviction being overturned by higher courts after appeal due to violation of constitutional rights.

In the dissenting opinion for Smith v. Illinois, Justice John Marshall Harlan II argued that the majority's decision to overturn Smith's conviction based on a violation of his Sixth Amendment right was incorrect. He believed that there was no constitutional requirement for an accused person to be informed of their right to confront witnesses against them at every stage of trial proceedings. Instead, he asserted that this right should only apply during critical stages where substantial rights might be lost if counsel is not present. In this case, he did not believe such a situation had occurred and thus disagreed with the majority’s ruling in favor of Smith.