An administrative law judge or presiding officer has the authority to sequester witnesses.  Sequestration of witnesses means separation of witnesses.  Witnesses are ordered out of the courtroom except for their time on the stand.  Witnesses are also cautioned not to discuss their testimony with other witnesses.  Sequestration is intended to assure that the witnesses will testify based on their own knowledge of the facts without being influenced by testimony of prior witnesses.  Witness sequestration also seeks to strengthen the role of cross-examination in developing facts. 

Judges sometimes refuse to sequestrate or exclude witnesses who are parties because parties have the right to participate fully in the hearing.  Pursuant to USCS Fed Rules Evid R 615, a person whose presence is shown by a party to be essential to the presentation of the party’s cause cannot be excluded.  Moreover, if there is no question about the credibility of witnesses or there is no demonstration of prejudice, failure to sequester witnesses is harmless.