Constitutional due process and double jeopardy protections affect the question of when a prosecutor can file new or different charges in a criminal case. Utah’s Rule 4(d) of the Rules of Criminal Procedure provides that a prosecutor can file an amended information with new, additional, or different charges any time prior to the beginning of a criminal trial, “so long as the substantial rights of the defendant are not prejudiced.” Jeopardy is considered to “attach” to a case once a jury is empaneled or, in a bench trial, when the first witness is called and sworn.
In order to comply with constitutional principles of due process, Rule 4 also requires that if the prosecutor files additional or different charges before trial, the defense is entitled to a continuance (additional time) to prepare to meet the new charges, and, if the new charges involve the right to a preliminary hearing (preliminary examination), that the court must grant a new preliminary hearing on the new or additional charges.