Legal analysis: 1, general prevention. It refers to perfecting various legal protection systems, carrying out various educational activities, advocating a good social atmosphere, improving the macro-social environment such as families and schools and the micro-environment of social institutions, resisting and eliminating the influence of various negative social factors, strengthening conditional preventive measures, and reducing the opportunities and conditions for crime.

2. Special prevention. It refers to taking special measures to prevent crimes, imprisoning and reforming criminals according to law, and preventing them from breaking the law again. Through the application of the death penalty, the criminals who commit the most heinous crimes are physically eliminated, and the possibility of committing crimes again is completely eliminated; Through the application of life imprisonment, criminals are isolated from society for life and deprived of the conditions for them to commit crimes again in society; Through the application of fixed-term imprisonment and educational reform, criminals can experience the pain of punishment personally and consciously eliminate the idea of breaking the law again.

3. Micro-prevention refers to setting up various defense lines to prevent and reduce social crimes and recidivism. Reduce the occurrence of crime by mobilizing people to actively participate in combating crime and preventing crime.

Legal basis: Article 87 of the Criminal Law of People's Republic of China (PRC). No prosecution will be initiated after the following time limit:

(1) After five years (2) after ten years (3) after fifteen years (4) after life imprisonment or death penalty. 20 years later, if it is deemed necessary to prosecute, it shall be submitted to the Supreme People's Procuratorate for approval.