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BENCH BLOG: Judges show Daubert isn’t all that complicated

Debate over expert witness testimony clarifies rule

Jean DiMotto is a retired Milwaukee County Circuit Court judge. She served for 16 years, and was on the criminal bench for 12 of those years.

Judge Jean DiMotto retired in 2013 after 16 years on the Milwaukee County Circuit bench and now serves as a reserve judge. She also serves of counsel with Nistler & Condon SC.

In the first Wisconsin case applying the Daubert standard on admissibility of expert witness testimony, the court of appeals explains “what the Daubert rule is and what it is not.”

Man in the road

The factual scenario in State v. Giese began when a woman found a man lying in the roadway at 2:12 a.m. She summoned law enforcement.

The “very intoxicated” man, Todd Giese, told a Washington County deputy he had crashed his car about three hours earlier, began to walk home and fell asleep in the road.

Giese could not recall his address or phone number. While he admitted he had earlier been at a tavern with friends, he could not recall the name of the tavern or the names of any of his friends.

Meanwhile, another deputy happened to pass the site of Giese’s crashed car. There were no intoxicants or alcohol containers in the car, nor were there any bars or restaurants along the three-mile stretch between his car and where Giese was lying in the roadway.

Blood alcohol concentration

Giese was transported to a medical center where a sample of his blood was drawn at 3:30 a.m. The state crime lab’s analysis revealed a blood alcohol concentration of 0.18.

Because Giese had been convicted of at least four prior drunken-driving offenses, his permissible blood alcohol concentration was 0.02.

Accordingly, Giese was charged with operating a motor vehicle while intoxicated, fifth or sixth offense, and operating with a prohibited blood alcohol concentration, fifth or sixth offense.

The prosecutor asked the crime lab’s toxicologist to do a retrograde extrapolation, that is, calculate Giese’s approximate BAC at the time he crashed his car. She was informed that the crash occurred about four hours before the blood sample was drawn.

Based on the facts from the investigation, the toxicologist made two assumptions: the alcohol was fully absorbed before the crash and no alcohol was ingested after the crash. She opined that Giese’s BAC was above 0.02 at the time of the crash.

Daubert hearing

Giese took issue with the toxicologist’s assumptions and with the reliability of retrograde or back extrapolation. He challenged admissibility of the toxicologist’s testimony under sec. 907.02 which codifies the Daubert rule. Therefore, Washington County Circuit Judge James Muehlbauer conducted a pretrial Daubert hearing.

The toxicologist testified about her education and experience, including her specific training with the “effect of alcohol dissipation and elimination.” She testified that she had performed back extrapolation in other cases.

She was familiar with books and studies on back extrapolation. She also was familiar with rates of alcohol absorption and elimination generally accepted in her peer community of forensic toxicologists.

Together with her two assumptions, the established rates of fast, slow and average rates of elimination formed the foundation of her back extrapolation on Giese’s BAC.

On cross-examination, she conceded that changes to her assumptions could alter her opinion. She recognized the expertise of a widely acknowledged expert who had written that “no forensically valid … extrapolation of blood … alcohol concentrations is ordinarily possible … solely on the basis of time and individual analysis results.”

She countered this statement by explaining that she had more than time and the one blood test result in Giese’s case: she had the “given scenario” and her two assumptions about the absorption of alcohol based on that scenario.

She acknowledged that one of the books in her training materials referred to back extrapolation as “a dubious practice given the variables at play.” On redirect it was shown that the same book discussed back-extrapolation methodology and that “peers in [her] field, toxicologists” testify about their calculations using this methodology.

Muehlbauer found the toxicologist’s testimony to be based on sufficient data from the factual scenario, and her assumptions to be plausible based on that scenario. He iterated that challenges to her assumptions could be made during cross-examination at trial since they went to the weight, not the admissibility, of her testimony.

Appellate analysis

A rare interlocutory appeal of Muelbauer’s nonfinal order was accepted. Judge Richard Brown of the District II Court of Appeals wrote the opinion.

The court explained that, assuming the expert’s opinion is probative, the Daubert gate-keeping function is to ensure that the expert’s principles and methodology are based on a reliable foundation “in the knowledge and experience of [the expert’s] discipline.”

The foundation must be more than conjecture or speculation. The Daubert rule forbids ipse dixit (“because I said so”) testimony.

Giese acknowledged there is a 2005, pre-Daubert, Wisconsin case approving retrograde extrapolation of BAC, but insisted that under Daubert, having only one blood analysis and an estimated time of driving does not meet the requirement for a reliable foundation.

In response, the court first looked out of jurisdiction for cases on retrograde extrapolation that applied Daubert. It found three cases where the calculation was determined to be a generally accepted scientific method, meeting the Daubert standard. There weren’t any that determined the methodology failed the Daubert standard.

Brown wrote that the record in Giese’s case “shows that despite certain doubts and disagreements, retrograde extrapolation is a widely accepted methodology in the forensic toxicology field.” Moreover, he noted, the crime lab’s toxicologist had more than just one blood test and an estimated time of driving to work with.

Other facts were: where Giese was found, when he was found, his statements about what had transpired, the absence of bars and restaurants along the route he walked and the absence of alcohol containers in his car or along the route. These facts undergirded the toxicologist’s two assumptions and made them plausible.

Since Daubert only concerns the admissibility of expert testimony, Brown again agreed with Muehlbauer that the weight of the testimony is handled by cross-examination.


As chief judge of the Wisconsin Court of Appeals, Brown appropriately shouldered authorship of the first published decision on Daubert since the 2011 codification of the rule in Wisconsin.

In a mere five paragraphs, he met his goal of explaining what the Daubert rule is and what it is not. He then applied that understanding to the particular science at issue in this case: retrograde extrapolation. He was able to accomplish both, including an out-of-jurisdiction case-law journey, in a 15-page decision.

The opinion guides the bench and bar well, and not just in these explanations. Brown also took care to give a detailed summation of the expert’s testimony at the Daubert hearing.

This allows us to follow along as if we were there, thus helping litigators understand how to present and vigorously challenge Daubert testimony, and helping judges formulate a ruling before learning of Muehlbauer’s decision.

Judges and lawyers dreaded the introduction of the Daubert rule in Wisconsin. Yet both Muehlbauer and Brown have shown that it is not so complicated after all.

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