1. Defence lawyers can provide legal aid 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. 2. 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. 3. Defence lawyers can meet and correspond with criminal suspects and defendants 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. 4. From the date when the people's procuratorate examines and prosecutes the case, the defense lawyer may consult, extract and copy the case file. Other defenders may also consult, extract and copy the above materials with the permission of the people's court or the people's procuratorate. Defenders have the right to apply to the people's procuratorate or the people's court for obtaining the evidence materials collected by the public security organs and the people's procuratorate to prove the innocence or light crimes of the criminal suspects and defendants during the investigation, examination and prosecution. 5. With the consent of the witness or other relevant units and individuals, the defense lawyer may collect materials related to the case from him, or apply to the people's procuratorate or the people's court to collect and obtain evidence, or apply to the people's court to notify the witness to testify in court. With the permission of the people's procuratorate or the people's court, and with the consent of the victim or his close relatives or witnesses provided by the victim, the defense lawyer may collect materials related to the case from them. 6. If the evidence collected by the defender shows that the suspect is not at the scene of the crime, has not reached the age of criminal responsibility, and belongs to a mental patient who is not criminally responsible according to law, he shall promptly inform the public security organ and the people's procuratorate. 7. A defender or other person shall not help a criminal suspect or defendant to conceal, destroy, forge evidence or confess, and shall not threaten or induce witnesses to commit perjury or engage in other acts that hinder judicial proceedings. To sum up, the defense lawyer is generally the lawyer invited by the defendant. As long as this lawyer is hired, it is necessary for the lawyer to provide legal defense for the client and help the client to reduce the corresponding criminal law or plead not guilty. Therefore, lawyers must also act according to their professional ethics.