Legal basis: People's Republic of China (PRC) Lawyers Law.
Article 35 An entrusted lawyer may, according to the needs of a case, apply to a people's procuratorate or a people's court to collect and obtain evidence, or apply to a people's court to notify witnesses to testify in court. If a lawyer investigates and collects evidence by himself, he may, with the lawyer's practice certificate and the certificate of the law firm, investigate the situation related to undertaking legal affairs with the relevant units or individuals.
Article 38 A lawyer shall keep the state secrets and business secrets he knows in his practice, and shall not disclose the privacy of his clients. Lawyers should keep confidential the relevant information and materials that their clients and others are unwilling to disclose in their practice activities. However, criminal facts and information that endanger national security, public safety and seriously endanger the personal safety of others are excluded.