Legal analysis: According to the provisions of China's Criminal Procedure Law, the period of criminal detention is the time when the public security department is collecting evidence and investigating cases, and it is also the time when the public security department has not decided whether to prosecute. The public security department transfers the case to the procuratorial department, and the procuratorial department brings a public prosecution to the court. Only after the court files a case can the lawyer intervene.
Legal basis: Article 33 of the Criminal Procedure Law of People's Republic of China (PRC). A criminal suspect has the right to entrust a defender from the day when he is interrogated for the first time by the investigation organ or takes compulsory measures. During the investigation, only lawyers can be entrusted as defenders. The defendant has the right to entrust a defender at any time.