California Code, Penal Code - PEN § 867

While a witness is under examination, the magistrate shall, upon motion of either party, exclude all potential and actual witness 1 who have not been examined.

The magistrate shall also order the witnesses not to converse with each other until they are all examined. The magistrate may also order, where feasible, that the witnesses be kept separated from each other until they are all examined.

This section does not apply to the investigating officer or the investigator for the defendant, nor does it apply to officers having custody of persons brought before the magistrate.

Either party may challenge the exclusion of any person under this section. Upon motion of either party, the magistrate shall hold a hearing, on the record, to determine if the person sought to be excluded is, in fact, a person excludable under this section.