(a) Complaint. The complaint is a signed written statement of the essential facts constituting the offense charged. A circuit court-district division complaint charging a class A misdemeanor or felony shall be signed under oath, provided that a complaint filed by a police officer, as defined in RSA 106-L:2, I, for a violation-level offense or a class B misdemeanor shall not require an oath. Unless otherwise prohibited by law, the court may permit a complaint to be amended if no additional or different offense is charged and if substantial rights of the defendant are not prejudiced.
(b) Issuance of Arrest Warrant. If it appears from a sworn application for an arrest warrant that there is probable cause to believe that an offense has been committed, and that the defendant committed