legal ground
Article 33 of the Criminal Procedure Law of People's Republic of China (PRC)
A criminal suspect or defendant may entrust one or two persons as defenders in addition to exercising the right of defense by himself. The following persons may be entrusted as defenders:
(1) lawyers;
(2) A person recommended by a people's organization or the unit to which the criminal suspect or defendant belongs;
(3) Guardians, relatives and friends of criminal suspects and defendants.
A person who has been sentenced to punishment according to law or deprived of or restricted personal freedom shall not act as a defender.
A person who has been dismissed from public office or has his lawyer's or notary's practice certificate revoked may not act as a defender, except the guardian or near relative of the criminal suspect or defendant.
Article 37
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.