The short answer to your specific question is no, the police are not required to interview the defendant prior to applying for a complaint. All that is needed for a complaint to issue is probable cause. Probable cause is a much lower degree of evidence than that needed for conviction. It simply means "reasonably trustworthy information sufficient to warrant a
prudent person in believing that a crime has been committed and that the accused is the
perpetrator." In a domestic violence situation that could be simply the statement of the complaining witness.
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Police questioning is not mandatory before a felony complaint can issue. All that is required is that the magistrate believe the police have porbable cause that a crime was committed and you committed the offense to justify a warrant being issued for your arrest. In Massachusetts, however, misdemeanors are crimes punishable by up to two and one-half years in jail and are usually tried in the District Court. Misdemeanor crimes are less serious than felonies and would require a magistrate to conduct a hearing prior to the issuance of any criminal charges if the alleged criminal act was not committed in the presence of the police officer. You would be given notice of the application for criminal complaint process which should have happened in your case since Assault is a misdemeanor, not a felony.