No. 23-1004 ___________________________

Tumey, LLP; Tod T. Tumey

Plaintiffs - Appellants

v. Mycroft AI, Inc.; Joshua Montgomery; Michael Lewis

Defendants - Appellees ___________________________

No. 23-1214 ___________________________

Tumey, LLP; Tod T. Tumey

Plaintiffs - Appellants

v. Mycroft AI, Inc.; Joshua Montgomery; Michael Lewis

Defendants - Appellees ____________

Appeal from United States District Court for the Western District of Missouri - Kansas City ____________

Submitted: September 21, 2023 Filed: October 24, 2023 ____________ Before SMITH, Chief Judge, MELLOY and ERICKSON, Circuit Judges. ____________ MELLOY, Circuit Judge.

Tod T. Tumey and Tumey, LLP (collectively, “Tumey”) appeal the district court’s1 denial of their motion to disqualify Mark Lanterman from serving as an expert witness. Appellants argue that Lanterman’s testimony should have been excluded due to a conflict of interest, and as a result of this error, the case should be reversed and remanded. We affirm.

I.

Tumey commenced this action in 2021, alleging that Mycroft AI, Inc., Michael Lewis, and Joshua Montgomery (collectively, “Mycroft”) engaged in harassment of Tumey, including through “online hacking, phishing, identity theft, and other cyberattacks.” In May 2021, Tumey contacted Mark Lanterman to inquire about employing him as an expert witness in the case. Tumey emailed Lanterman a copy of their Complaint against Mycroft, after which Tumey’s counsel and Lanterman had a forty-to-sixty-minute conference call to discuss the nature of the case and potential expert work involved. On the call, Lanterman shared that he had checked for conflicts of interest and would be available to serve as Tumey’s expert in the case. Tumey’s counsel and Lanterman also discussed: evidence Tumey had collected, Mycroft’s possible counterarguments and evidence, Tumey’s discovery and litigation strategies, a fake website Tumey created to “trap” potential hackers, the value of using forensic analysis in the case, Tumey’s other expert witness, and the law enforcement agencies that Tumey had contacted regarding the case. Lanterman was not compensated for his time on the conference call; afterward, Lanterman emailed Tumey an engagement letter that included a confidentiality

1 The Honorable Beth Phillips, Chief Judge, United States District Court for the Western District of Missouri. -2- provision. Tumey never executed the engagement letter and did not retain Lanterman.

In January 2022, Mycroft designated Lanterman as their expert witness, and Tumey moved to disqualify Lanterman on grounds that a conflict of interest existed based on the May 2021 emails and conference call. The district court denied Tumey’s motion to disqualify Lanterman, who later testified at trial. A jury found in favor of Mycroft. Tumey appealed the denial of the motion to disqualify Lanterman, asking this Court to reverse and remand the case for a new trial. We deny this request and affirm.

II.

We review a district court’s denial of a motion to exclude expert testimony for an abuse of discretion, and we review “its findings of fact for clear error.” Taylor v. Cottrell, Inc., 795 F.3d 813, 816 (8th Cir. 2015). A court abuses its discretion “if it ‘commits a clear error of judgment in weighing [the relevant] factors.’” Nutt v. Kees, 796 F.3d 988, 991 (8th Cir. 2015) (quoting Gen. Motors Corp. v. Harry Brown’s, LLC, 563 F.3d 312, 316 (8th Cir. 2009)).

In denying Tumey’s motion to disqualify Lanterman as a