legal ground
Article 87 of the criminal law
After the following time limit, the crime will not be prosecuted:
(1) Five years have passed if the statutory maximum penalty is less than five years of fixed-term imprisonment;
(2) Ten years if the statutory maximum penalty is fixed-term imprisonment of not less than five years but not more than ten years;
(3) Fifteen years if the statutory maximum penalty is fixed-term imprisonment of not less than ten years;
(4) Twenty years have passed if the maximum legal punishment is 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.