The silent witness rule is the use of "substitutions" when referring to sensitive information in the United States open courtroom jury trial system. An example of a substitution method is the use of code-words on a "key card", to which witnesses and the jury would refer during the trial, but which the public would not have access to. The rule is an evidentiary doctrine that tries to balance the state secrets privilege with the bill of rights (especially the right of the accused to a public trial, and the right to due process). In practice the rule has been rarely used and was often challenged by judges and civil rights advocates. Its use remains controversial.
 The conflict between the open court and state secrets privilege goes back to at least 1802 and Marbury v. Madison. Under the privilege, the government can dismiss any charges against it by claiming that important state secrets would be revealed at trial. In 1980 the Classified Information Procedures Act (CIPA) was passed as an attempt to deal with the conflict, especially the problem of graymail. The silent witness rule (SWR) is a further attempt.
 By 2011 the government had only attempted to use the rule a handful of times, often unsuccessfully:
 In United States v. Rosen, in 2007 (the AIPAC Espionage Act case), the rule was used for the first real time. The government tried to use the rule extensively at first; the court rejected the idea.
 Rosen argued that the rule was invalid because he felt it did not match CIPA requirements, and that the government had said CIPA was the only way to deal with classified information at a trial. The judge for the trial, T. S. Ellis III, disagreed that CIPA was the only acceptable way to deal with classified information. He also felt that the SWR was not really part of CIPA either.
 Ellis created a four-part "fairness test" to decide whether the SWR was fair. His test was a combination of the CIPA fairness test and the Press-Enterprise Co. v. Superior Court fairness test. Ellis' theory was based on the idea that the SWR effectively "closes a trial" from the public by disclosing different sets of evidence to the court and to the public. The four parts of his test were as follows:
 Judge Ellis decided that the Rosen case met the fairness test, and approved use of the SWR at trial. It was used for 4 minutes 6 seconds of playback of a conversation. However, Ellis sealed (kept secret) the exact way that the SWR figured into the proceedings.
 Lamb argues that the silent witness rule would enable trials to go ahead that would otherwise be dismissed because of the state secrets privilege. He especially points out El-Masri v. Tenet, in which a German citizen was allegedly kidnapped and raped by CIA agents but was never allowed to present his case in court, and United States v. Reynolds, in which widows of Air Force contractors sued the government; both cases were dismissed because the government claimed the trial would reveal national secrets.
 The rule has received media coverage for its suggested use by the government in United States v. Drake (2010). Bishop, in the Baltimore Sun, writes that lawyers say the "secret codes quickly become confusing and risk violating the defendant's constitutional rights to a public trial". Jesselyn Radack of the Government Accountability Project called it an "oxymoron", and pointed out that it "would still allow jurors to see classified information, defeating the whole purpose of classification". Josh Gerstein at Politico wrote that it might create conflict between the prosecution and the news media.