Article 124 of the Criminal Procedure Law stipulates that the period of investigation and detention of a criminal suspect after arrest shall not exceed two months. If the criminal suspect has been detained before arrest, the detention period shall not be included in the investigation detention period. Under normal circumstances, the investigation organ shall end the investigation within the time limit for investigation and detention prescribed by law. The special detention period refers to the extension of the investigation detention period, but it must meet the legal conditions and perform the corresponding examination and approval procedures. The main situations are: 1. According to the provisions of Article 124 of the Criminal Procedure Law, if the case is complicated and cannot be concluded at the expiration of the time limit, it may be extended by 1 month with the approval of the people's procuratorate at the next higher level. 2. According to the provisions of Article 125 of the Criminal Procedure Law, if it is not suitable for long-term trial for special reasons, especially for major and complicated cases, the Supreme People's Procuratorate shall report to the NPC Standing Committee to postpone the trial. 3. According to the provisions of Article 126 of the Criminal Procedure Law, if the investigation cannot be concluded after the expiration of the time limit stipulated in Article 124 of the Criminal Procedure Law, it may be extended for two months with the approval or decision of the people's procuratorate of the province, autonomous region or municipality directly under the Central Government: (1) Major and complicated cases in remote areas with very inconvenient traffic; (2) Major criminal group cases; (3) Major and complicated escape criminal cases; (4) Major and complicated cases involving a wide range and difficulties in obtaining evidence. 4. According to Article 127 of the Criminal Procedure Law, the suspect may be sentenced to more than 10 years in prison. If the investigation cannot be concluded after the extension period expires in accordance with the provisions of Article 126 of this Law, it may be extended for another two months with the approval or decision of the people's procuratorate of the province, autonomous region or municipality directly under the Central Government. According to the provisions of Article 30 and Article 3 1 of the Regulations on Six Organs, if a public security organ requests to extend the detention period of a case, it shall submit it seven days before the expiration of the detention period, and submit the main facts of the case and the specific reasons for extending the detention period in writing. The people's procuratorate shall make a decision before the expiration of the detention period. The cases directly put on file for investigation in the Supreme People's Procuratorate meet the conditions stipulated in Articles 124, 126 and 127 of the Criminal Procedure Law. If it is necessary to extend the detention period of a criminal suspect, it shall be decided by the Supreme People's Procuratorate according to law.