legal ground
Article 37 of the Criminal Procedure Law of People's Republic of China (PRC)
The responsibility of a defender is to provide materials and opinions on whether a criminal suspect or defendant is innocent, light or relieved of criminal responsibility according to facts and laws, and to safeguard the litigation rights and other legitimate rights and interests of the criminal suspect or defendant.
Article 40
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.
Article 43
With the consent of witnesses or other relevant units and individuals, defense lawyers may collect materials related to the case from them, 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 witnesses 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.