Saturday, July 02, 2005

Colorado Supreme Court Waxes Mathematical

Here's a dispatch from James England, our Colorado correspondent:
In a potentially far-reaching opinion, the Colorado Supreme Court on June 27, 2005, affirmed a trial court's exclusion of ergonomics testimony offered by a criminal defendant, finding that the expert's characterization of his opinion as being "more likely than not" was insufficiently supported by "empirical or methodological justification." See People v. Wilkerson, No. 04SA362 (Colo. June 27, 2005).

The defendant was charged with attempted first degree murder when a handgun discharged, accidentally, according to her. Her attorney endorsed a professor of ergonomics to testify about his general analysis of accidental shootings. Because the expert had not tested the actual handgun, it appears that his analysis was based on the defendant's account of the shooting and his opinion was essentially limited to stating that general factors of her account were consistent with an accidental shooting. The prosecution conceded, and the trial court agreed, that the expert was "eminently qualified" to testify in this field.

On cross-examination at a pre-trial Daubert hearing, the expert characterized his opinion as being that it was "more likely than not" that the shooting was accidental, and agreed that his reference to "likely" was the same as "more than 50 percent." The trial court then ruled that the defense could not present such expert testimony at trial, apparently criticizing the lack of any "body of literature or knowledge concerning standards of measuring" accidental shootings and "error rates" associated with such analysis.

In an interlocutory review of this order, a five-Justice majority of the Colorado Supreme Court affirmed the exclusion of the expert testimony. Although expressing some criticism of the underlying factual foundation for the expert's opinion, the majority instead based its decision on the lack of "empirical or methodological justification in the record" for the expert's supposed "numeric calculation of the possibility that the shooting in this case was accidental." The two dissenting judges attacked this analysis, pointing out that the expert had not expressed any actual mathematical probabilities supporting his conclusion, but had merely agreed on cross-examination that he believed his opinion was more probable than not.

In Colorado, judges typically require any expert opinion to be couched in terms of "reasonable probability." That is, a medical expert, must testify that his or her diagnosis is based on a "reasonable degree of medical probability." This decision may require a foundational showing of some "empirical or methodological justification" that would establish the actual existence of such probability.
That block quotation is Mr. England's take. Here's ours, which should not be imputed to him.

The notion sometimes arises that whenever experts characterize their opinions by reference to probability, they are advancing quantitative probabilistic claims that must be gauged against formal statistical standards. That notion seems plainly fallacious, because "probability" has more than one meaning. It's simply wrong to impose a formal statistical one on expert testimony that neither claims nor depends on a primarily statistical basis. Similar confusion over testimony offered to a "reasonable medical [or scientific] certainty" seems to arise much more rarely, perhaps because nearly everybody understands that testimony need not really be indisputable to be admissible. Yesterday, for example, we reported on a case involving a handwriting expert who said she held her opinion to a "reasonable degree of scientific certainty." The Third Circuit was justly dismissive of the idea that such language imported a requirement of utter indubitability.

Someday, we may post a more extended discussion of the spurious mathematicization of legal standards that can arise when Daubert collides with verbiage associated with the burden of persuasion, or with "magic language" that state law may prescribe for experts describing the confidence with which their opinions are held. In the interim, we hope that Wilkerson does not foreshadow a general Colorado trend.


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Fed. R. Evid. 702: If scientific, technical, or other specialized knowledge will assist the trier of fact to understand the evidence or to determine a fact in issue, a witness qualified as an expert by knowledge, skill, experience, training, or education, may testify thereto in the form of an opinion or otherwise, if (1) the testimony is based upon sufficient facts or data, (2) the testimony is the product of reliable principles and methods, and (3) the witness has applied the principles and methods reliably to the facts of the case.