legal ground
Article 59 of the Criminal Procedure Law
The people's procuratorate shall prove the legality of evidence collection in the process of court investigation. If the existing evidence materials cannot prove the legality of evidence collection, the people's procuratorate may request the people's court to notify the relevant investigators or other personnel to appear in court to explain the situation; The people's court may notify the relevant investigators or other personnel to appear in court to explain the situation. Relevant investigators or other personnel may also request to appear in court to explain the situation. Upon notification by the people's court, the relevant personnel shall appear in court.
Article 62
Anyone who knows the case has the obligation to testify. A person who is physically and mentally defective or young, can't distinguish right from wrong and can't express correctly, can't be a witness.