物证鉴定范式发展(一):传统明确结论范式

Forensic Paradigm Development.Part 1:The Traditional Paradigm of Categorical Conclusions

物证鉴定范式是解释物证结果证据意义并形成鉴定意见过程中采用的科学理论和方法。物证鉴定领域正在经历从传统的物证来源明确结论范式向物证结果似然比评估范式转换。传统物证鉴定范式以特征唯一性作为科学基础假设,已有100余年发展和应用历史,应用于除DNA物证以外的几乎所有物证。鉴定人通过检测和比对物证和样本特征确定二者特征是否匹配,并采用阈值决策方式给出物证和样本来源相同或来源不同意见。基于物证明确来源意见和案件其他证据信息,决策者再做出相关的行为事实推论,作为被告犯罪与否的中间证据事实。在传统范式中,鉴定人从物证和样本特征结果得到物证明确来源意见的过程是一个演绎推理过程:大前提是物证特征唯一性假设,小前提是特征匹配(或不匹配)结果,结论是物证和样本来源相同(或不同)。只要大前提和小前提为真,传统范式的来源明确意见就正确。然而,随着DNA物证结果概率评估方法的发展和成熟,一些学者质疑特征唯一性假设缺少实证证明,进而认为失去这一前提的传统范式的演绎推理无效,因此传统物证来源明确意见范式被认为缺少坚固的科学基础。

The forensic paradigm is the scientific theories and methods used in the process of interpreting thefindings of forensic examination and forming expert opinion.There is a paradigm shift from the traditional paradigm of categorical source conclusions to the paradigm of evaluative opinion.The traditional forensic paradigm is based on the assumption of feature uniqueness.The traditional paradigm of forensic science has a history of over 100 years of development and application,and has been applied to almost all physical evidence except DNA evidence.After detecting and comparing trace evidence from crime scene and known source sample,examiner will determine whether the features of the trace evidence match features of the sample,and will use threshold decision-making to give opinions on the trace evidence and the sample came from a same source or from different sources.In the traditional paradigm,the process by which examiner forms a categorical source opinions from results of the features is a deductive reasoning process:the major premise is the assumption of the uniqueness of trace features,the minor premise is the results of feature matching(or no-match),and the conclusion is that the trace and sample has same(or different)source.As long as the major and minor premises are true,the categorical opinion on source of the traditional paradigm is correct.However,with the development and maturity of evaluative methods for forensic DNA results,some scholars questioned the lack of empirical proof for the hypothesis of feature uniqueness in the traditional forensic paradigm,and thus believe that deductive reasoning without a major premise of the assumption of the trace features uniqueness has no validity,and therefore,the categorical source opinion in the traditional paradigm lacks a solid scientific foundation.