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Uncertain Rule Of Certainty: An Analysis And Proposal For A Federal Evidence Rule, The , Michael M. Martin

Faculty Scholarship

Two characteristic principles of Anglo-American evidence law are the requirement that witnesses testify only to their personal observations (the "first-hand knowledge" rule) and the prohibition against witnesses testifying to their inferences (the "opinion" rule). However, a longstanding exception to these principles permits witnesses possessed of skill or learning to draw inferences, often from facts they have not personally observed. Because such expert opinion testimony is exceptional, it is hedged about with various restrictions in addition to those such as relevancy which apply to all testimony. The predicate for admission of expert opinion testimony generally consists of two elements. First, the …