Legal basis: Article 36 of the Criminal Procedure Law of People's Republic of China (PRC), defense lawyers can provide legal assistance to criminal suspects during investigation; Acting as an agent for complaints and accusations; Apply for changing compulsory measures; Ask the investigation organ about the crimes and cases suspected by the criminal suspect, and put forward opinions. Article 37 A defense lawyer may meet and correspond with a criminal suspect or defendant in custody. Other defenders, with the permission of the people's courts and people's procuratorates, may also meet and correspond with criminal suspects and defendants in custody. If a defense lawyer holds a lawyer's practice certificate, a law firm's certificate, a power of attorney or a letter of legal aid to ask for a meeting with the criminal suspect or defendant in custody, the detention center shall arrange the meeting in time, which shall not exceed 48 hours at the latest. In cases of crimes endangering national security, terrorist activities and particularly serious bribery crimes, defense lawyers should obtain permission from the investigation organ when meeting with the criminal suspect in custody during the investigation. The investigation organ shall notify the detention center of the above situation in advance. When a defense lawyer meets a criminal suspect or defendant in custody, he can understand the case and provide legal advice. From the date when the case is transferred for examination and prosecution, the relevant evidence may be verified with the criminal suspect or defendant. Defense lawyers are not monitored when meeting with criminal suspects and defendants. The provisions of paragraphs 1, 3 and 4 shall apply to the meetings and correspondence between defense lawyers and criminal suspects and defendants who are under surveillance.