Forensic Paradigm Development.Part 1:The Traditional Paradigm of Categorical Conclusions
The forensic paradigm is the scientific theories and methods used in the process of interpreting the findings 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.
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