Traditional criminal trial activities include

Judicial investigation is initiated by the court, that is, the court thinks that the criminal suspect should be arrested, and investigation should be carried out before deciding to arrest. Criminal investigation is carried out by public security organs, that is, criminal crimes are investigated, and then compulsory measures are taken against criminal suspects, and the procuratorial organs are invited to approve the arrest. The criminal procedure law stipulates that. Investigation refers to the special investigation and relevant compulsory measures implemented by public security organs and people's procuratorates in the process of handling cases according to law. Investigation is a basic and independent litigation stage in criminal proceedings and a necessary procedure for public prosecution cases. Only after investigation can a public prosecution case be decided whether to prosecute or try. Therefore, the Criminal Procedure Law stipulates that public security organs should investigate criminal cases that have been filed. The purpose of investigation is to collect and obtain evidence of the suspect's guilt or innocence, whether the crime is light or heavy. Investigation is also a kind of investigation, but it is not only different from administrative investigation and general social investigation, but also different from other litigation investigations, such as the investigation of the people's court in the process of handling cases. It is a preparatory activity for the investigation organ to find out the case, arrest the suspect and collect all kinds of evidence to decide whether to prosecute the suspect after a criminal case is filed.