In Smith v. Illinois, the U.S. Supreme Court rules that a defendant’s Sixth Amendment right to confront witnesses against him is violated when a prosecution witness is identified only by an assumed name and refuses to provide his real name or address. The Court finds that without such basic information, the defendant’s ability to have his counsel effectively cross-examine the witness is damaged. Most notably, defense counsel cannot conduct a thorough investigation into the background and reputation of the witness, evidence that could help damage the witness’s credibility and could help the defendant’s case.