We’ve all seen police procedurals on TV where investigators keep witnesses or suspects away from each other so they can’t get together to keep their stories straight. For essentially the same reason, judges may do something similar with witnesses at trials, ordering them to stay away from the trial before they testify to keep them from hearing each other’s testimony. Witness exclusion orders (sometimes called witness sequestration or separation orders) may also forbid certain behavior outside of the courtroom. However, they may not prevent defendants or some other witnesses from attending the trial.

Why Sequester Witnesses?

Witness exclusion orders are intended to prevent witnesses from tailoring their testimony based on what other witnesses have said. This helps the jury ferret out the truth by noticing inconsistencies in the testimonies of different witnesses.

When Do Judges Exclude Witnesses From the Courtroom?

Under federal court rules, judges must exclude witnesses whenever it’s requested by one of the parties (the defendant, the prosecutor, or, in a civil case, the person who filed the lawsuit). They may also decide to issue exclusion orders on their own. (Fed. R. Evid. 615 (2019).) States have similar rules. In some states, however, judges aren’t required to grant a request to sequester witnesses; instead, they have the power to decide whether the order is needed.

Usually, judges issue witness exclusion orders at the beginning of trial, before any testimony. But when it’s appropriate, they may decide to exclude witnesses after the trial has gotten underway or during pretrial hearings.

Do Exclusion Orders Cover Out-of-Court Communications?

Courts disagree about whether the federal and state rules on witness exclusion orders cover conduct outside of the courtroom—like talking to other witnesses or reading transcripts of their testimony—that could frustrate the purpose of the order. But even if it can’t be assumed that any witness sequestration order applies to anything other than attending the trial, judges may add specific restrictions on witnesses’ out-of-court communications.

Are Any Witnesses Exempt From Exclusion Orders?

Criminal defendants have a constitutional right to be present in the courtroom during all the testimony. So even if they plan to take the stand, judges may not exclude them. Federal and most state rules also exempt certain other witnesses from exclusion orders, including:

• either party, or the representative of a party that’s not a person (like the government)
• a witness whose presence at the trial is essential to present the party’s case, such as the lead law enforcement investigator in a criminal case; or
• anyone who’s authorized to be at the trial under law.

Expert witnesses aren’t necessarily exempt from exclusion orders, but lawyers often argue that they need their help during the trial because of their specialized knowledge.

Some states give crime victims the right to attend the entire trial.

What Are the Penalties for Violations of Witness Exclusion Orders?

When witnesses violate exclusion orders, the judge may come up with appropriate measures, such as:

• allowing the lawyer for the other side to cross-examine the witness about the violation and challenge the witness’s credibility
• explaining to the jurors how they should evaluate the witness’s credibility in light of the violation
• citing the witness (and any lawyers who were responsible for the violation) for contempt of court
• disqualifying the witness from testifying, or
• declaring a mistrial, ordering a new trial, or reversing the judgment.

Most courts agree that judges shouldn’t use the last two types of penalties except in extraordinary situations where other corrective actions can’t address the potential harm to a fair trial. When deciding whether to prevent the witness from testifying, a judge should consider how serious the violation was, whether allowing the witness to testify would probably affect the outcome of the trial, and whether the party who called the witness was responsible for the violation.

Barring witness testimony because of an exclusion-order violation raises particular constitutional issues in criminal trials where the offending witness was scheduled to testify for the defense. After all, it’s generally not fair to prevent defendants from putting on a strong defense and call witnesses because of actions by others.

In the reverse scenario, where criminal defendants claim that prosecution witnesses disobeyed orders, courts have held that the defendants are entitled to a hearing on the issue (U.S. v. Engelmann, 701 F.3d 874 (8th Cir. 2012)). And judges may be more likely to impose harsh penalties on the prosecution, especially if the witnesses had help from government lawyers. In one famous example, during Zacarias Moussaoui’s trial related to the 9/11 attacks, the judge ordered that witnesses could not attend or follow the trial (including by reading transcripts) before they testified. After a government lawyer provided seven key witnesses with transcripts of other witnesses’ previous testimony, the judge barred any testimony from those seven witnesses.