The medical expert, junk reasoning, and junk science in personal injury litigation.

Technical and scientific evidence and the use of experts in the courts have increased in past decades. The courts' and juries' evaluation of such evi dence, as to its underlying method, degree of proof, overall quality, and the distinction of what is and is not science, can be difficult. There must be an understanding of the methods of science, of proof, and, most im portantly, of the difference among speculative, marginal, and established knowledge. Courts can be inundated by technical and unfamiliar infor mation and terminology, scientific publications, and abstruse concepts. Ex perts are given a wide range in which to express their opinions, and their persuasiveness may be determined more by credentials or personality than by the quality of their reasoning or the scientific status of the evidence. As a result, spurious issues can be brought before a court and can lead to confusion and to less-than-scientific decisions. The law, as a prime and professional evaluator of evidence, has to determine what is science, whether a method or an opinion is scientific, what criteria can be applied to individual issues, and how that criteria will assist the adjudication pro cess. Although these criteria have arisen in different jurisdictions, they share certain features, namely, a general acceptance within the scientific community, a recognizable place and coherence within a larger organized body of knowledge, a reliability of technique and its proper application, and an awareness of the degree of error of the technique. Such criteria permit the identification of evidence that falls below the standards of sci ence and is sometimes referred to as "junk science." These criteria evolved primarily in criminal and toxic tort cases and have led to legal judgments