According to incomplete statistics, there are at least 16 million people with severe mental illness in China, including about 16-32 thousand cases with violent tendencies, and new mental patients are still being produced every year. In criminal cases, because of the weak self-control of the mentally ill, the crime has the characteristics of unspecified object, location, time and cruelty, which are different from other general criminal cases, and this kind of crime is a serious hidden danger to public safety. So, what causes people with serious mental illness to commit crimes and other violent acts? The presence of mentally ill persons who cause accidents and crashes in society is not an isolated phenomenon. This particular group of people is different from the rest of society in that they not only pose a serious danger to society, but this danger is difficult to foresee. It has been reported that people with serious mental illnesses cause about 10% of all injuries. Therefore, we should strengthen the management of this special group of people. Yang Yong, Psychiatry Department, Suzhou Guangji HospitalÂ