Abstract: By combination of quantitative evidence support and the five-level propositional framework, the Bayesian Likelihood Ratio model is considered to be the mainstream international scientific evidence evaluation paradigm. In China, the application of Bayesian Likelihood Ratio model in the evaluation of DNA evidence is facing a triple challenge: At the technical level, there are problems such as difficulties in the separation of mixed samples, allele dropout, and model uncertainty; At the institutional level, the current normative documents regard uncertainty as a technical flaw, forcing appraisers to issue “pseudo-certainty” conclusions; At the cognitive level, the fact finder is prone to fall into “numerical absolutes” due to the lack of statistical knowledge; At the institutional level, the current regulatory documents regard uncertainty opinions as technical defects, forcing experts to issue “pseudo-certainty” conclusions; At the cognitive level, the fact-finder is prone to fall into “numerical absolutism” due to lack of statistical knowledge. Based on this, the study proposes a multi-dimensional improvement path: developing high-precision algorithms and optimizing mixed-sample analysis, constructing dynamic genetic databases to reduce model bias, revising judicial norms to recognize the reasonableness of uncertainty expression, and establishing a hierarchical review standard for “technical uncertainty” and “cognitive uncertainty”. The aim is to improve the practical application value of DNA evidence and promote the accuracy and fairness of scientific evidence evaluation in court.

Key words: DNA evidence, evidence evaluation, likelihood ratio

摘要： 贝叶斯似然比模型通过量化证据支持度与五级命题框架的结合，被认为是国际主流的科学证据评价范式。在我国，贝叶斯似然比模型在DNA证据评价中的应用面临三重挑战：技术层面存在混合样本分离困难、等位基因缺失及模型不确定性等问题；制度层面现行的规范性文件将不确定性意见视为技术瑕疵，迫使鉴定人出具“伪确定性”结论；认知层面事实认定者因统计知识匮乏易陷入“数值绝对主义”误判。基于此，研究提出多维完善路径：开发高精度算法并优化混合样本分析，构建动态遗传数据库以减少模型偏差；修订司法规范以承认不确定性表述的合理性，建立“技术性不确定”与“认知性不确定”分级审查标准。以期提高DNA证据的实际应用价值，促进法庭科学证据评价的准确性和公正性。

关键词: DNA证据, 证据评价, 似然比