A case in which the parties are suspected of a criminal offence and meet the statutory conditions for filing a case, and the people's procuratorate needs to file a case for investigation or prosecution. For ordinary criminal cases, which are under the jurisdiction of public security organs, the public security organs need to file a case. Then, what if the Economic Investigation Brigade files a case but does not arrest people? During the period of economic investigation, the public security organs may take compulsory measures such as criminal detention or arrest if they meet the requirements. Filing a case refers to the litigation activities that the public security, judicial organs and other administrative law enforcement organs decide to investigate or try as a criminal case after reviewing the materials such as reporting, accusation, report, surrender and private prosecution according to their respective jurisdictions, and when they think that criminal facts have occurred and need to be investigated for criminal responsibility. After the public security organ decides to file a case for investigation, it can decide when to arrest people according to the needs of the case. There is no specific time limit. Under normal circumstances, when the case is put on file for investigation, the suspect is already in the detention center. After a person is arrested, he shall be detained first and transferred within 30 days.