Owners of stolen property shall mainly recover it through judicial organs in accordance with the "Criminal Law", "Criminal Procedure Law", "Public Security Management Punishment Law" and other relevant laws.
② If the items are not recovered and the thief is let go by the police station, you can sue the Xinzhou police for malfeasance in their duties.
Whether the police letting these people go without authorization constitutes a crime of dereliction of duty, please refer to the provisions of the Criminal Law:
Article 400: Judicial staff secretly release criminal suspects and defendants Or if the criminal is remanded for retrial, he shall be sentenced to fixed-term imprisonment of not more than five years or criminal detention; if the circumstances are serious, he shall be sentenced to fixed-term imprisonment of not less than five years but not more than 10 years; if the circumstances are particularly serious, he shall be sentenced to fixed-term imprisonment of not less than 10 years.
If a judicial staff member causes a criminal suspect, defendant or criminal in custody to escape due to serious irresponsibility, causing serious consequences, he shall be sentenced to fixed-term imprisonment of not more than three years or criminal detention; if the consequences are particularly serious, he shall be sentenced to three years. Fixed-term imprisonment of not less than ten years but not more than ten years.
You cannot file a lawsuit against the police as part of a criminal investigation. But you can report it to the procuratorate, which can investigate the malfeasance after filing the case.
By the way, a reminder: Isolated evidence is invalid. Another key is that you should keep good evidence and it is best not to deal with the police alone.