In Daubert: Very Convoluted, Usually Confusing to Many, Nevertheless Elegant, Armand Rossetti writes that it is the expert witness in the first instance, and not the court as gatekeeper, who is the judge of what resources to choose to assist her in forming an opinion. It is the expert who will initially filter out prejudicial information as being irrelevant. The Court then uses Rule 703 to assure the reliability of evidence by vetting the bases that forms an expert’s testimony.
Let’s take environmental asbestos infiltration an example, the fact that an air sampling study is an associational (or case) study affecting a few subjects, rather than a higher evidence based epidemiological study that affects several hundred subjects should not bar an expert from using the case study to inform her opinion about the dangers of asbestos release in the environment. The fact that a single case study published in a peer reviewed journal fails to establish causation under a Rule 703 review should go to the weight that the jury will give such evidence, but it does not mean that an expert cannot eventually rely upon it in part to form an ultimate opinion.
Of course, if a single case study were the only source of evidence, then the court might be reasonable in immediately performing a Rule 702 analysis to disqualify the entire testimony. However, the fact that an expert has relied upon several case studies to form an opinion, and has not used even one single epidemiological study should not in itself disqualify that expert’s testimony.
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