Opinions are usually inadmissible as evidence in a trial. However, for hundreds of years, our Anglo-American common law jurisprudence has admitted expert opinion testimony on matters that are beyond the understanding or knowledge of the average lay person on a jury. There are two predicates for admissibility of opinion testimony. First, it must be relevant to the issues in the trial and, second, the opinion must be reliable, i.e., it must come from someone who is knowledgeable in the field in which the opinion is being expressed and must be scientifically valid.
Countiss et al. (Sun,) studied this question.
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