Lapsley v. Xtek, Inc., 689 F.3d 802 (7th Cir. 2012):

This appeal arose from an accident at a steel rolling mill that permanently disabled one of the workers there. The circumstances of that accident were unusual. Industrial grease was propelled in a jet with enough energy to penetrate and pass through the human body like a bullet. That jet hit and disabled plaintiff Leonard Lapsley. At trial the jury found that the accident was caused by a design defect in a heavy industrial product designed and manufactured by defendant Xtek, and sold and installed in the mill. That equipment contained an internal spring that could exert over ten thousand pounds of force. The jury accepted the theory of plaintiffs' expert witness, Dr. Gary Hutter, that the spring was the culprit mechanism behind the accident and that an alternative design of a thrust plate in the equipment would have prevented the disabling accident. Xtek has appealed, challenging the district court's denial of its Daubert motion that sought to bar Dr. Hutter from offering his expert opinions, which were essential to the plaintiffs' case.

The purpose of the Daubert inquiry is to scrutinize proposed expert witness testimony to determine if it has "the same level of intellectual rigor that characterizes the practice of an expert in the relevant field" so as to be deemed reliable enough to present to a jury. Kumho Tire Co. v. Carmichael, 526 U.S. 137, 152, 119 S. Ct. 1167, 143 L. Ed. 2d 238 (1999). A Daubert inquiry is not designed to have the district judge take the place of the jury to decide ultimate issues of credibility and accuracy. If the proposed expert testimony meets the Daubert threshold of relevance and reliability, the accuracy of the actual evidence is to be tested before the jury with the familiar tools of "vigorous cross-examination, presentation of contrary evidence, and careful instruction on the burden of proof." Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579, 596, 113 S. Ct. 2786, 125 L. Ed. 2d 469 (1993). Once the district court has adequately applied the Daubert framework, our review of the determination to admit or exclude the evidence is deferential. E.g., United States v. Lupton, 620 F.3d 790, 798-99 (7th Cir. 2010) (affirming exclusion of expert testimony); see also Kumho Tire, 526 U.S. at 152 (reversing court of appeals decision that failed to accord sufficient discretion to district court that admitted expert testimony). In this case, the district court's stated analysis of the proposed testimony was brief, but it was also directly to the point and was sufficient to trigger deferential review on appeal. We affirm the judgment of the district court. ***

II. Daubert and Causation

Determining the true facts of a case often requires "the application of some scientific, technical, or other specialized knowledge." Fed. R. Evid. 702, advisory committee's note to 1972 proposed rules. Federal Rule of Evidence 702 permits testimony by qualified experts where such testimony will help the trier of fact understand the evidence or decide the factual issues. As the Rule 702 committee notes and Rules 703 to 705 make clear, an expert may give an opinion to the jury concerning the facts, subject to cross-examination on the work forming the basis of that opinion, or may, less frequently, "give a dissertation or exposition of scientific or other principles relevant to the case, leaving the trier of fact to apply them to the facts." Id. Rule 702 requires that expert testimony be relevant, reliable, and have a factual basis -- requirements that must be met before the jury is allowed to hear and perhaps be persuaded by the expert testimony. As the Supreme Court explained in Daubert, the trial judge must make a determination at the outset whether these factors are satisfied by the proposed testimony. 509 U.S. at 592-93. Under Rule 702, the trial judge stands as a gatekeeper to prevent irrelevant or unreliable testimony from being admitted.

Screening evidence pre-trial is a function squarely within the purview of the trial judge. We review a district court's decision to admit or exclude expert testimony for abuse of discretion, without substituting our own judgment for the district judge's exercise of discretion. E.g., Kunz v. DeFelice, 538 F.3d 667, 675 (7th Cir. 2008). We review de novo, however, the district court's understanding and proper application of the multi-factor Daubert framework. For example, in Metavante Corp. v. Emigrant Savings Bank, 619 F.3d 748, 760 (7th Cir. 2010), we applied de novo review where the court "failed to perform a Daubert analysis" and articulated only a one-sentence conclusion. See also Naeem v. McKesson Drug Co., 444 F.3d 593, 608 (7th Cir. 2006) (declining to apply deferential review where district court provided no analysis of methodology in its one-sentence determination). Similarly, we refused to defer to a conclusory Daubert determination in Fuesting v. Zimmer, Inc., 421 F.3d 528, 534-35 (7th Cir. 2005), modified on rehearing on other grounds, 448 F.3d 936 (7th Cir. 2006), though we repeated the general rule: "Provided the district court adhered to Daubert's parameters, we will not disturb the district court's findings unless they are manifestly erroneous."

The parties here disagree about whether the district court's brief written analysis of Dr. Hutter's testimony was sufficient to justify deferential review. We find that it was.

Xtek relies heavily on ATA Airlines, Inc. v. Federal Express Corp., 665 F.3d 882 (7th Cir. 2011), in which we found erroneous the admission of a regression analysis that was based on only the district court's (correct) statement that regression is a widely accepted method. In fact, there were "grave questions concerning the reliability" of the expert's specific calculations. We noted that neither side's lawyers successfully conveyed their own understanding of the regression analysis they were arguing about. Id. at 889. As Lapsley points out, however, ATA Airlines did not change the standard of review established in our cases for appeals from Daubert decisions.

The district judge here did more than state the general acceptability of Dr. Hutter's methods and calculations. The judge provided specific examples that show he reviewed and understood the basis for Dr. Hutter's conclusions. As our discussion below makes clear, the math and science here are within the comprehension of judges and lawyers without extraordinary assistance. Xtek disputes the completeness and therefore the relevance of Dr. Hutter's calculations, but it has not identified, and we have not detected, any grave questions about the reliability of the calculations actually performed by Dr. Hutter. Under these circumstances, the district court's brief application of the Daubert framework is sufficient to warrant the deferential review we give it below. ***

We do not agree that Dr. Hutter's method and calculations were insufficiently detailed or inherently opaque to the district court or the lawyers here. We do not find, and the district court did not find, Dr. Hutter's analysis to be as difficult to understand as Xtek suggests. Lawyers and judges who were not trained in science can benefit from the famous "Two Cultures" lecture given in 1959 by British scientist and novelist C. P. Snow, in which he described the cultural gap between persons schooled in the sciences and those schooled in the humanities:

A good many times I have been present at gatherings of people who, by the standards of the traditional culture, are thought highly educated and who have with considerable gusto been expressing their incredulity at the illiteracy of scientists. Once or twice I have been provoked and have asked the company how many of them could describe the Second Law of Thermodynamics. The response was cold: it was also negative. Yet I was asking something which is about the scientific equivalent of: Have you read a work of Shakespeare's?

Law must apply itself to the life of a society driven more and more by technology and technological improvements. Judges and lawyers do not have the luxury of functional illiteracy in either of these two cultures. Sometimes, as in this case, effective presentation, cross-examination, and evaluation of expert testimony require lawyers and judges to fill in gaps in their scientific, engineering, or mathematics educations or refresh their memories about them. We see no indication, either from the district court's Daubert ruling or its later discussions of the expert evidence during trial, of any deficiency in the court's preparation or in its understanding of the proposed evidence.

Dr. Hutter's calculations to support his theory of causation were attached to his report and made available to Xtek's counsel and the district judge prior to his ruling on Xtek's initial Daubert motion. Those calculations apply principles of classical mechanics commonly taught in high school physics classes. His notes, mistakenly disparaged by Xtek as "the instructive equivalent of Sanskrit," are in fact relatively straightforward to comprehend for those familiar with these basic mechanical principles and with the rudiments of scientific notation. If they appear opaque to some readers, it is more likely because of the "Two Cultures" problem rather than any inadequacy of presentation. As with most informal work-product, the notes could have been even clearer and more self-explanatory, but Xtek's lawyers and the district judge all had opportunities to ask Dr. Hutter to explain his calculations. Based on the written submissions, the district judge here did not feel the need to question Dr. Hutter directly, and Xtek did not request that he hold a hearing to do so.