Legal analysis: A letter of understanding does not have to be signed to be valid. It must be signed by the victim. A criminal understanding generally refers to a written document of a legal nature issued by the victim to reach a settlement regarding the outcome of the criminal case and the suspect or his family. The letter of understanding is usually completed from the filing of a public prosecution to the cross-examination in court, and it has the effect of discretionary mitigation and leniency in criminal law.

Legal basis: "Criminal Procedure Law of the People's Republic of China" Article 289 If the two parties reconcile, the public security organs, People's Procuratorate, and People's Court shall hear the opinions of the parties and other relevant persons opinions, review the voluntariness and legality of the settlement, and preside over the preparation of the settlement agreement.