United States v. Lewis

Decision Date03 March 2020
Docket NumberCriminal No. 18-194 ADM/DTS
Citation442 F.Supp.3d 1122
Parties UNITED STATES of America, Plaintiff, v. Kenneth Davon LEWIS, Defendant.
CourtU.S. District Court — District of Minnesota

This matter is before the undersigned United States District Judge for a ruling on Defendant Kenneth Davon Lewis' ("Lewis") Objection [Docket No. 119] to Magistrate Judge David T. Schultz's January 6, 2020 Report and Recommendation [Docket No. 115] ("R&R"). In the R&R, Judge Schultz recommends denying in part and granting in part Lewis' Motion to Exclude DNA Evidence [Docket No. 27]. For the reasons stated below, the Objection is overruled and the R&R is adopted.


The full background of this motion is thoroughly set forth in the R&R and is incorporated by reference. Briefly, Lewis faces trial after being federally indicted on one count of being an armed career criminal in possession of a firearm. See Superseding Indictment [Docket No. 126]. Lewis was arrested on April 18, 2018 after scuffling with police officers and a landlord in the stairwell of an apartment building. R&R at 1132–33. A Smith & Wesson 9mm gun was recovered at the scene. R&R at 1131–32, 1132–33.

After Lewis' arrest, the gun was sent to Midwest Regional Forensic Laboratory ("MRFL") for DNA testing. The MRFL lab analyzed three DNA swabs1 from the gun using a probabilistic genotyping software program called STRmix. Gov't Ex. 1 at 2; Gov't Ex. 19.2 Each of the analyzed swabs contained a large amount of "good quality" DNA. Tr. Vol. III [Docket No. 83] at 456.

Based on the STRmix analysis, the MRFL lab determined the DNA on the gun was a mixture from four persons. Gov't Ex. 1 at 2; Def. Ex. 6 at 1. The STRmix results showed that the DNA mixture in each of the three swabs is "greater than one billion times more likely if it originated from [Lewis] and three unknown unrelated individuals than if it originated from four unknown unrelated individuals." Gov't Ex. 1 at 2. This statistic, called a likelihood ratio ("LR"), is interpreted as providing "extremely strong support for inclusion" of Lewis as a contributor to the DNA mixture found on the gun. Id. Lewis was determined to be the highest contributor and was estimated to have contributed 56% to the DNA mixture. Def. Ex. 6 at 1; Tr. Vol. II [Docket No. 60] at 166–67. The lowest contributor was estimated to have contributed 6% to the mixture. Def. Ex. 6 at 1.

The STRmix results also showed that all involved police officers and the landlord were excluded as contributors to the DNA mixture on the gun. Gov't Ex. 1 at 2. No likelihood ratio was provided for this result. See id.

Lewis challenges the admissibility of the DNA evidence, arguing the use of STRmix to analyze the DNA samples at issue is not sufficiently reliable to be admissible under Daubert v. Merrell Dow Pharms., Inc., 509 U.S. 579, 113 S.Ct. 2786, 125 L.Ed.2d 469 (1993). Judge Schultz conducted three days of evidentiary hearings and heard testimony from several experts, including Dr. John Buckleton. Dr. Buckleton is the co-developer of STRmix, which was created in 2011 through a joint venture that included New Zealand's Institute of Environmental Science and Research ("ESR"), where Dr. Buckleton serves as lead scientist. Tr. Vol. I [Docket No. 53] at 7, 12–13. Testimony was also heard from Anne Ciecko, the DNA technical leader at the MRFL lab. Tr. Vol. II at 127. Three defense experts also testified: Nathaniel Adams, a software engineer who reviews and analyzes forensic DNA testing results; Dr. Dan E. Krane, Ph.D., professor of biological sciences at Wright State University and president of Forensic Bioinformatics, Inc.; and Dr. Mats Heimdahl, professor of computer science at the University of Minnesota. Id. at 299–300; Tr. Vol. III at 378–79, 555–56; Def. Exs. 18, 25, 33.

Additionally, Judge Schultz appointed Dr. William Thompson as a special master to advise the Court on the issues of scientific reliability. See Order [Docket No. 77]. Dr. Thompson is a professor emeritus in the University of California–Irvine's Department of Criminology, Law & Society. Thomspon CV [Docket No. 114]. He also chairs the Human Factors Committee and is a member of the Forensic Science Standards Board of the Organization of Scientific Area Committees, which is sponsored by the National Institute of Standards and Technology. Id. He has written numerous articles on the topic of forensic DNA evidence. Id. Dr. Thompson reviewed the transcripts and exhibits from the first two days of testimony and personally attended the third day, during which he had the opportunity to ask questions of the witnesses. Dr. Thompson provided a Special Master's Report [Docket No. 113] to the Court on October 31, 2019. The Report was shared with the parties prior to their submission of post-hearing briefs. R&R at 1134–35.

On January 6, 2020, Judge Schultz issued a 63-page R&R finding that STRmix meets Daubert admissibility standards as to the DNA evidence of inclusion—that is, the evidence regarding the likelihood that Lewis is a potential contributor to the DNA mixture on the gun. As to the DNA evidence of exclusion—that is, the evidence excluding the police officers and landlord as potential contributors to the DNA mixture—Judge Schultz determined this DNA evidence falls below STRmix's established threshold for reliability. The R&R thus recommends denying Lewis' Daubert motion as to the evidence of inclusion, and granting the motion as to the evidence of exclusion. Lewis objects to the determination that the DNA evidence of inclusion is admissible. There were no objections to the conclusion that the evidence of exclusion is inadmissible.

A. Standard of Review

In reviewing a magistrate judge's report and recommendation, the district court "shall make a de novo determination of those portions of the report or specified proposed findings or recommendations to which objection is made." 28 U.S.C. § 636(b)(1)(C) ; see also D. Minn. L.R. 72.2(b). A district judge "may accept, reject, or modify, in whole or in part, the findings or recommendations made by the magistrate judge." 28 U.S.C. § 636(b)(1)(C).

B. Daubert Standard

The admission of expert testimony is governed by Rule 702 of the Federal Rules of Evidence, which provides:

A witness who is qualified as an expert by knowledge, skill, experience, training, or education may testify in the form of an opinion or otherwise if: (a) the expert's scientific, technical, or other specialized knowledge will help the trier of fact to understand the evidence or to determine a fact in issue; (b) the testimony is based on sufficient facts or data; (c) the testimony is the product of reliable principles and methods; and (d) the expert has reliably applied the principles and methods to the facts of the case.

When evaluating the admissibility of expert testimony, a trial court serves as the gatekeeper to "ensure that any and all scientific testimony or evidence admitted is not only relevant, but reliable." Daubert v. Merrell Dow Pharms., Inc., 509 U.S. 579, 589, 113 S.Ct. 2786, 125 L.Ed.2d 469 (1993).

"In a case involving scientific evidence, evidentiary reliability will be based on scientific validity ." Id. at 590 n.9, 113 S.Ct. 2786 (emphasis in original). A trial court may consider one or more of the following non-exclusive factors in assessing scientific validity: "(1) whether the theory or technique can be (and has been) tested; (2) whether the theory or technique has been subjected to peer review and publication; (3) the known or potential rate of error; and (4) whether the theory has been generally accepted [in the relevant scientific community]." Lauzon v. Senco Prods., Inc., 270 F.3d 681, 687 (8th Cir. 2001) (citing Daubert, 509 U.S. at 593–94, 113 S.Ct. 2786 ). A district court possesses broad discretion in making its reliability determination. Kumho Tire Co. v. Carmichael, 526 U.S. 137, 142, 119 S.Ct. 1167, 143 L.Ed.2d 238 (1999). The proponent of the expert testimony bears the burden of showing by a preponderance of the evidence that the testimony is admissible. Lauzon, 270 F.3d at 686.

"As a general rule, the factual basis of an expert opinion goes to the credibility of the testimony, not the admissibility, and it is up to the opposing party to examine the factual basis for the opinion in cross-examination." United States v. Finch, 630 F.3d 1057, 1062 (8th Cir. 2011) (internal quotations and alterations omitted). Although Rule 702 favors admissibility rather than exclusion, the district court must ensure that an expert's testimony "rests on a reliable foundation." Daubert, 509 U.S. at 597, 113 S.Ct. 2786.

C. Lewis' Objections

Lewis raises three objections to the R&R's conclusion that STRMix evidence of Lewis' inclusion as a potential contributor to the DNA mixtures meets Daubert's admissibility standard. Lewis argues: 1) STRMix has not demonstrated foundational validity; 2) STRMix has no known error rate; and 3) STRMix did not follow minimum software industry practices to ensure its software performed reliably.

1. Foundational Validity

Lewis argues STRmix has not been shown to be a sufficiently reliable method for analyzing the type of complex DNA mixtures at issue here. Lewis contends that validation studies show the range of reliability for STRmix does not extend beyond DNA mixtures involving more than three contributors in which the minor contributor constitutes less than 20%. The DNA mixtures at issue here each involve four contributors with the minor contributor constituting 6%. Def. Ex. 6 at 1. Lewis thus contends these mixtures exceed the bounds of reliability which have been validated for STRmix.

Lewis largely relies on a 2016 report by the President's Council and Advisors on Science and Technology ("PCAST") that addressed the validity and reliability of probabilistic genotyping software programs such as STRmix. Def. Ex. 2. The PCAST Report examined the...

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