It is a practical problem closely related to the credibility of forensic appraisal to judge the validity of appraisal entrusted by parties themselves. As an important means for parties to obtain evidence, the qualification of appraisal entrusted by parties as evidence has been recognized by law, but the rule of reviewing its weight of proof has been in a vague state for a long time. The main reason is that the nature is not clear, and there are long-standing theoretical disputes regarding the nature of forensic appraisal, such as expert opinion, witness testimony, documentary evidence and parties' statement. In view of the strict proof system mainly adopted in China, if a certain evidence material is excluded from the statutory evidence category, it will not be able to clarify the rule of evidence review and judgment. Therefore, it is necessary to classify the appraisal entrusted by the parties into the most similar legal evidence category, namely documentary evidence. However, different from ordinary documentary evidence, the review of evidence validity of private appraisal opinion focuses on its weight of proof, and the review process should be divided into four stages: evidence presentation, preliminary confirmation of weight of proof, cross-examination, and final confirmation of weight of proof. In addition, compared with other evidence, appraisal entrusted by court or by administration is generally of greater probative force than that entrusted by parties themselves, while the appraisal entrusted by the parties unilaterally is weaker than that entrusted by the parties jointly, but it should still be analyzed in specific cases.
