Legal basis: Provisions on Procedures of Public Security Organs in Handling Criminal Cases Article 57 Public security organs must collect all kinds of evidence that can prove the guilt or innocence of criminal suspects and the seriousness of the crime according to legal procedures. It is necessary to ensure that all citizens who are related to or know the case have the conditions to provide evidence objectively and fully, and they can be hired to assist in the investigation except in special circumstances. Article 365 of the Procedures for Handling Criminal Cases by Public Security Organs: The scope of criminal judicial assistance and police cooperation by public security organs mainly includes the exchange and cooperation of criminal intelligence information, investigation and evidence collection, delivery of criminal litigation documents, collection of evidence materials such as physical evidence, documentary evidence, audio-visual materials or electronic data, extradition, arrest and expulsion of criminal suspects, defendants or criminals, and other matters of criminal judicial assistance and police cooperation as stipulated in international treaties and agreements.