Criminal cases refer to cases in which criminal suspects and defendants are accused of violating social relations protected by criminal law, and the state conducts investigation, trial and criminal sanctions in order to investigate the criminal responsibility of criminal suspects and defendants. Criminal cases have the following characteristics: 1, and the external manifestation is direct infringement; 2. Most cases have obvious crime scenes; 3. The causality of the case is complex and diverse; 4. The formation of the case is staged and sudden.