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Retrograde extrapolation of blood alcohol concentration survives Daubert challenge

State v. Todd J. Giese, 2014 WI App 92; case activity

Expert testimony regarding retrograde extrapolation of Giese’s blood alcohol concentration is admissible under new version of § 907.02(1) despite the fact some experts doubt its reliability because it was the product of reliable principles and methods and based upon sufficient facts and data.

Giese, who was charged with operating while intoxicated and with a prohibited alcohol content, challenged the admissibility of a retrograde extrapolation of his BAC by the state’s toxicologist. The BAC of the drawn blood was 0.181, but the extrapolation concluded his BAC was at least 0.221 at the time he was driving, which was 4 to 4.5 hours before blood was drawn. (¶¶3-8, 15). Giese cited the opinion of an acknowledged expert (Kurt Dubowski) that “no forensically valid forward or backward extrapolation of blood or breath alcohol concentrations is ordinarily possible in a given subject and occasion solely on the basis of time and individual analysis results.” (¶10). He also argued that even if extrapolation is reliable in general, it can’t reliably be applied to the facts and data of this case, and that the state could not prove the facts underlying its expert’s opinion—namely, the time of the driving, the time of the drinking, and that no drinking occurred between the time of the driving and the time of the blood test. (¶¶10, 21, 24).

After a quick summary of the new expert admissibility regime ushered in by 2011 Wis. Act 2, which adopted the rule from Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579 (1993) (¶¶17-20), the court holds the retrograde extrapolation satisfies the requirements of § 907.02(1). First, the general methodology of extrapolation is widely accepted and no court has held it fails to meet the Daubert standard. (¶¶22-23). And:

¶23      …. The mere fact that some experts may disagree about the reliability of retrograde extrapolation does not mean that testimony about retrograde extrapolation violates the Daubert standard. If experts are in disagreement, it is not for the court to decide “which of several competing scientific theories has the best provenance.” Ruiz-Troche v. Pepsi Cola of P.R. Bottling Co., 161 F.3d 77, 85 (1st Cir. 1998). …

The court then dismisses Giese’s claim that the cases admitting retrograde extrapolation are distinguishable from his because in those cases the expert had two blood tests and/or a known time of driving or drinking to work with, while in this case the toxicologist had only a single test result, an estimated time of driving, and two assumptions—that the alcohol was fully absorbed by the time of the driving and that Giese drank nothing after driving. (¶24). The court concludes:

¶25      …. Despite Giese’s assertions to the contrary, the record confirms that the expert had more to work with here than a single test result. A number of known facts made the expert’s assumptions plausible—Giese was found lying in a roadway at 2:12 a.m.; he said he had crashed his vehicle three hours earlier, started walking away from the scene, and fell asleep in the road; there were no bars or restaurants along the route he walked and no alcohol containers found in his car or along that route; and his blood sample drawn an hour or so later had a blood alcohol concentration of .18.  


28      We think Giese’s real dispute is not with the science the expert relied upon in his case but with the assumptions the expert made. It is true that the calculation would be more reliable if the expert had more facts about exactly when and what Giese drank. However, under the circumstances, we think Giese’s questions go to the weight of the evidence, not to its admissibility. See [State v.] Burgess5 A.3d 911, 916  [(Vt. 2010)] (“concerns [about the reliability of retrograde extrapolation] relate to the proper weight to be afforded the evidence, not whether the evidence is admissible in the first place”). Giese remains free to challenge the accuracy of the expert’s assumptions. He may, for instance, propose competing scenarios—e.g., that Giese drank all the alcohol soon before driving. Or that he began drinking alcohol, or continued drinking, after the crash. In our adversary system, “[j]uries resolve factual disputes” like those. State v. Abbott Labs.2012 WI 62, ¶69, 341 Wis. 2d 510, 816 N.W.2d 145 (citation omitted); see also Daubert, 509 U.S. at 596 (“Vigorous cross-examination, presentation of contrary evidence, and careful instruction on the burden of proof are the traditional and appropriate means of attacking shaky but admissible evidence.”). Giese still has the chance to undermine the assumptions that support the expert’s opinion by introducing evidence or arguing in favor of competing inferences from the known facts. But the expert’s opinion is admissible under Daubert.

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