PUBLISH
UNITED STATES COURT OF APPEALS
FOR THE TENTH CIRCUIT

________________ _________________ NATHAN PETERSEN, Plaintiff - Appellant,

v. THE RAYMOND CORPORATION, Defendant - Appellee. No. 20-4026

________________ _________________ Appeal from the United States District Court for the District of Utah (D.C. No. 2:14-CV-00894-RJS)

________________ _________________ Michael J. Warshauer of Warsha uer Law Group, P.C., Atlanta, Georgia (David A. Cutt of Eisenberg Cutt Kendell & Olson, Salt Lake City, Utah, w ith him on the briefs), for Plaintiff-Appellant. Francis H. LoCoco of Husch Blackwell LLP, Milwaukee, Wi sconsin (Rick L. Rose and Kristine M. Larsen, of Ray Quinney & Nebeke r, Salt Lake City, Utah , with him on the brief), for Defendant-Appellee.

________________ _________________ Before TYMKOVICH , Chief Judge, BALDOCK , and CARSON , Circuit Judges.

________________ _________________ CARSON , Circuit Judge.

________________ _________________ The district court serves as a gatekeep er, shutting the door on unreliable expert testimony. See Kumho Tire Co., Ltd. v. Carmichael, 526 U.S. 137, 152 (1999). And we afford district courts “considerable leeway” in deci ding when the door should be FILED United States Court of Appeals Tenth Circuit 

### April 22, 2021 Christopher M. Wolpert Clerk of Court2 closed. Id. Plaintiff Na than Petersen (“Plaintiff” ) argues the district court impermissibly closed the door on the strict products liability clai m he brought against Defendant Raymond Corpora tion (“Raymond”) alleging it defectively manufactured a forklift. In support of his claim he sought to offer expe rt testimony that the forklift would be safer if it had “a door” on it. The district cour t found the expert’s testimony unreliable and excluded it. It then granted a related motion for summary judgment in Raymond’s favor. Plaintiff appeals. Exercising jurisdiction under 28 U.S.C. § 1291, we affirm.
I. Plaintiff injured himself while opera ting the Raymond Model 4200 stand-up counterbalance lift truck (“Raymond forkli ft”). The Raymond forklift has an open compartment. So it does not fully enclos e the operator’s lower extremities. When Plaintiff lost control of th e Raymond forklift, his left leg slid out of the open compartment and he crushed it against warehouse racking. Plaintiff sued the Raymond forklift manufacturer—Raymond—alleging strict liability. Plaintiff asserted the Raym ond forklift’s open compartment made it defective. And he tried to offer expert testimony from Plai ntiff’s expert in support of that assertion. Plaintiff’s expert concluded that a dding a door could cure this deficiency. But Plaintiff’s expert did not commit to the specific type of door he believed necessary. Instead , he offered that any num ber of doors would have worked.3 Raymond moved to exclude Plaintiff’s expe rt’s testimony. It then moved for summary judgment, arguing that Plaintiff c ould not meet his burden without expert testimony. Before ruling on these motions, the district court reviewed Plaintiff’s expert’s 76-page report and ordered supplemental cross br iefing on the admissibility of his opinions. It also held three evid entiary hearings wher e Plaintiff’s expert testified about his opinions. After review, the district court issu ed an extensive oral ruling excluding Plaintiff’s expert’s testimony that, in general, a door pres ented a safer, alternative design option. It reasoned that although Plai ntiff’s expert was qualified to offer this opinion, he failed to offer a specific safer, alternative desi gn and thus failed to reliably support his opinion. Because Plai ntiff lacked expert testimony that a safer, alternative design existed at the time of his injuries, he could not meet his burden for a Utah strict liability clai m. So the district court granted summary judgment in Raymond’s favor. Plai ntiff appeals.
II. The district court delivered its decision excluding Plaintiff’s expert in an oral ruling that lasted nearly two hours. The ruling lack ed some precision, making appellate review more difficult, but we see no need to remand for clarification. We review a district court’s decisi on to exclude testimony for abuse of discretion. See Bitler v. A.O. Smith Corp ., 400 F.3d 1227, 1232 ( 10th Cir. 2005). So we will not “disturb a district court’s ruling absent our conviction that it is arbitrary,4 capricious, whimsical, manifestly unreasonable , or clearly erroneous .” Id. (citing Goebel v. Denver and Rio Grande W. R.R. Co., 346 F.3d 987, 990 (10th Cir. 2003)). We review de novo a distri ct court’s grant of summary judgment. Allen v. Minnstar, Inc., 8 F.3d 1470, 1476 (10th Cir. 1993). The district court must grant summary judgment only if th e “moving party is entitled to judgment as a matter of law.” Fed. R. Civ. P. 56(c). Because this case arises out of diversity, we apply Utah law. Allen, 8 F.3d at 1476.
III.
A. In determining whether an expert may testify under Federal Rule of Evidence 702, the district court must first consid er whether the expert’s proffered testimony has “a reliable basis in the knowledge and experience of his discipline.” Daubert v. Merrell Dow Pharms., Inc., 509 U.S. 579, 592 (1993). When making this determination, the district court s hould examine “whether the reasoning or methodology underlying the testim ony is scientifically valid . . . .” Id. at 592–93. The district court excluded Plaintiff’s e xpert’s opinions for tw o reasons. First, Plaintiff’s expert failed to definitively offer a specific safer, alternative design. Second, he failed to relia bly support his opinion that any door would be a safer, alternative design. We will address each reason in turn. We conclude the district court did not abuse its discretion in ex cluding Plaintiff’s e xpert’s opinions, and therefore affirm its grant of summa ry judgment in Raymond’s favor.5 Under Utah law, a plaintiff bringing a st rict products liability claim must show that at the time of the in jury an “alternative, safer design, practicable under the circumstances” existed. Allen, 8 F.3d at 1479. Plaintiff argues the district court unlawfully found that Utah law limits a pl aintiff to offering only one alternative design. But the district cour t did not make such a finding. In fact the district court explicitly referenced that sometimes “multiple design op tions are warranted.” ROA
at 1932. The district court found that Plain tiff’s expert failed to commit to any definitive feasible design alternative. 1 And it rightfully excluded his testimony on that basis. The Fifth Circuit upheld a dist rict court’s exclusi on of expert testimony for the same reason in Guy v. Crown Eq uip. Corp. 394 F.3d 320, 323 (5th Cir. 2004). 2 In Guy, a plaintiff operating a fork lift with an open compartment lost control, and her left leg came out of the compartment and she crushed it. Id. The

1 The district court made multiple comme nts to this effect when issuing the oral ruling. ROA at 1917, 1918, 1919–1 920, 1921 & 1925–1926. But on whole the message remained the same, th e district court believed Pl aintiff’s counsel took “the unworkable and unfair position that they need not select a specific safer alternative design to enable Raymond, the jury, and th is court to compare the open back design they criticize with the pr oposed alternative.” ROA at 1894 (emphasis added).

2 In Guy, the plaintiff brought strict liability claims under the Mississippi Products Liability Act (“MPLA”). 394 F.3d at 322–23. The MPLA requires the plaintiff to show the existence of “a feasib le design alternative that would have to a reasonable probability prevented the harm.” M ISS . C ODE A NN . § 11-1-63(f)(ii). Although the MPLA defines “feasible design alternative” and Utah does not, the MPLA’s requirement is sufficiently analogous to Utah’s strict liability requirement that a plaintiff show a safer, alternative design existed at the tim e of the plaintiff’s injury.6 plaintiff brought a strict liability claim ag ainst the forklift manuf acturer. Id. In support of her claim she s ought to have an expert te stify that the forklift was defective, in part, because it lacked “an oper ator restraint (similar to a seat belt)[.]” Id. As a design alternative, the expert advocated use of a “restraining device” but “never presented a specific de sign.” Id. at 327. The district court excluded the expert’s testimony because the expert “h ad not presented any definitive theory, opinion or . . . feasible design al ternative . . . that could be te sted . . . .” Id. at 323. The Fifth Circuit held the district court acted within its disc retion in excluding the expert’s testimony because a lthough the expert suggested devices like those already on the market would suffice, “he never su bmitted a complete ‘end product.’” Id. at 327. “‘The proper methodology for prop osing alternative designs includes more than just conceptualizing po ssibilities[,]’” so the expert’s failure to offer a specific alternative rendered his tes timony inadmissible. Id. (q uoting Watkins v. Telsmith, Inc., 121 F.3d 984, 992 (5th Cir. 1997)). Like the Guy plaintiff, Plaintiff he re operated a forklift with an open compartment. He lost cont rol, his left leg came out of the compartment and he crushed it. Plaintiff’s expe rt, like the Guy expert, never presented a definitive safer, alternative design. In fact, he made a point not to commit to any specific design. He only advocated the use of “a door” a nd offered conceptualized possibilities. 3 The

3 In his expert report, Berry offe red as his alternative design that— The lift truck could have been provi ded with several designs of doors including, but not limited to, a latchi ng rear door, a spring loaded door,7 district court here, like the di strict court in Guy, excluded expert testimony for failure to present any testable defini tive design. The district court did not limit Plaintiff’s expert to submitting only one design. But it did require that Plai ntiff’s expert offer at least one definitive safer, alternative design. Without a definiti ve design, neither Plaintiff’s expert nor the district court could meaningfully compare any proffered design with the existing design. And neith er could a jury. For this reason, the

a magnet controlled door, and an inte rlocked door to provide further protection to operators from additiona l hazards. Properly designed doors that exist in the marketplace ri ght now, or which could be easily manufactured (see the Elrod door) woul d have a negligible effect on the maintenance of the machine. The door should have been constructed out of a suitable material that woul d withstand the forces of impact generated during collisions, intrus ions, tipovers and off-the-dock accidents. (Intrusion protection is not the primary purpose of the door needed to protect Mr. Peterson so wh ile intrusion protection is helpful, it is not essential to improve the sa fety of the machine so long as the door will assist the ope rator in keeping his le g inside the operator’s compartment.) The cost of provi ding such a rear door would be insignificant relative to the cost of the forklift. The cost of adding a latching rear guard to the Raymon d 420-C50QM would have cost at most $250 if designed and installed at the time of manufacture rather than as an add-on. Berry did not commit to any type of door , material of door, cost of door. He also does not specify how a manufactur er would add “a door” to the Raymond forklift despite admitting th at to put a door on a forklift you would need to know where the hinges went. He did admit, howev er, that “rugged hinges [were] available for use.” But again, he ne ver stated that he would us e rugged hinges here. He only offers that rugged hinges ex ist. He did not specify th e measurements for “a door” despite admitting that one would have to know whether the door spanned the entrance. He did not discuss how a ma nufacturer may hook the door up to the forklift’s electrical and comp uter systems despite admitti ng that someone would need to know whether such a hookup was possible. He also said he had not designed a specific door for the Raymond forklift. Defendant’s counsel asked Berry in a hearing, “[d]o you have any engineering drawings to show us of your design of a door for [the Raymond forklift] ?” Berry responded, “[n]o.”8 district court did not abuse its discretion in excluding Pl aintiff’s expert’s testimony for failure to offer any specific sa fer, alternative design.
B. Plaintiff argues the district court’ s misunderstanding of Utah law—on how many alternative designs a plaintiff can adva nce—permeated its ruli ng that Plaintiff’s expert did not offer a scientifically reliable expert opinion. Not true. Again, the true issue is not numerosity, it is design specificity. Because Pl aintiff’s expert offered no specific design, he did not test any speci fic design on the Raymond forklift, nor did he cite testing done by others of a specific design on the Raymond forklift. Plaintiff makes two assertions, neither of which advances the ball. First, Plaintiff asserts Plaintiff’ s expert did not have to test “a door” on the Raymond forklift himself. Although Rule 702 did not require Plaintiff’s expert to do the testing himself, we have upheld the exclusi on of an expert’s testimony for lack of sufficient methodology and r easoning where the expert reli ed on published material rather than testing his theory directly. See United States v. Ga baldon, 389 F.3d 1090, 1099 (10th Cir. 2004). And other circuits have excluded expert testimony on that same basis in forklift cases specifically. See Brown v. Raymond Corp., 432 F.3d 640, 647–48 (6th Cir. 2005) (concluding that an expert witness’s failu re to provide evidence of testing on his own alternative design justified th e district court’s ruling to exclude testimony); Dhillon v. Crown Controls Corp., 269 F.3d 865, 869–70 (7th Cir. 2001) (“We could identify a number of probl ems with the testim ony these witnesses were prepared to offer, but the most glar ing among them is the lack of testing, or9 more generally the failure to take any step s that would show professional rigor in the assessment of alternative de signs[.]”). We recognize “tes ting is not necessary in all instances to establish reliab ility under Daubert . . . .” Bitler, 400 F.3d at 1236. But the district court did not exclude Plaintiff’s expert’s opinion just because he did not test any door on the Raymon d forklift himself. Second, Plaintiff asserts that disagreement between experts does not warrant the exclusion of either expert’s testimony. See Feliciano-Hill v. Principi, 439 F.3d 18, 25 (1st Cir. 2006) (“The mere fact that two experts disagree is not grounds for excluding one’s testimony.”). Plaintiff argues that desp ite Raymond’s disagreement with Plaintiff’s expert’s opinions, Plaintif f’s expert did the re quisite analysis and testing for a reliable and t hus admissible opinion. But the district court did not exclude Plaintiff’s expert’s testimony b ecause experts could differ on whether adding a door would on whole be a safer alterna tive design. The district court found Plaintiff’s expert’s opi nions unreliable because Plaintiff’s expert fail[ed ] to say how he consider ed [the various doors listed in his report], fail[ed] to id entify any scientific or technical analysis he applied to each, or any of them, and offer[ed] no scientific support for his naked conc lusion that each or any of them is safer than the Raymond design. ROA at 1919. For a jury to find an al ternative design “safer” than the Raymond design, a comparative analysis must be possi ble. See Restatement (Third) of Torts, Prod. Liab. § 2 cmt. d (1997) (“Assessment of a product design in most instances requires a comparison between an alternat ive design and the product design that caused the injury . . . .” ). And so Plaintiff ha d to offer at least one definitive10 competing design. See Allen, 8 F.3d at 14 80–81 (“[I]n showing that the product can be made safer through the use of devices, a plaintiff must show that the devices exist and are not merely speculative .” (internal quotation marks and citation omitted)). A jury cannot compare the existing design to, essentially, anything and everything else. Plaintiff’s expert did not commit to any door design. True, Plaintiff’s expert included photos of some doors that exist in the real world in his expert report. But the district court did not abuse its discre tion in concluding that existence of these doors in the world, with nothing more, wa s insufficient. See Guy, 394 F.3d at 327; Brown, 432 F.3d at 647–48; Dhillon, 269 F.3d at 869–70. Without commitment to any design, Plai ntiff’s expert offered only sweeping opinions about doors in general. Plaintiff’ s expert argued that he could put a door on the Raymond forklift, but he had never done so. He opined that a manufacturer should construct a door “out of a suitable material that would withstand the force of impact” but he did not say what constituted a suitable material. He contended that the “cost of providing such a rear door would be insignificant re lative to the cost of the forklift” but he did not offer any numerical values aside from a pr ojection for the cost of adding a latching rear door . But again, he never co mmitted to a latching rear guard as an alternative design. So he offered this valuation only as a general example. Plaintiff’s expert also cited a 1991 st udy showing egress time only increased minimally when a manufacturer added a door to a forklift. But Plaintiff’s expert offered no evidence of which forklifts the 1991 study tested, under what11 circumstances the study tested the forklifts, or what pot ential consequences exist because of the minimal increase in egress time. Plaintiff’ s expert also cites a report showing egress time diminished where manufact urers added a spring loaded door to a forklift. Again, this data is not apparently specific to a dding a spring loaded door to the Raymond forklift and Plaintiff’s expert fails to explain th e circumstances under which the study tested the spring-loaded d oor. Even so, Plaint iff’s expert never committed to a spring loaded door as an alternative design. Other circuits have found expert testim ony unreliable where the expert failed to test a proposed alternative design on the specific forklift at issue. See Dhillon, 269 F.3d at 869–70 (holding th at the experts’ method ology unreliable because “[a]lthough both experts wanted to assert that the truck design was defective because it did not include a rear door, neither expert ha[d] actually designed a model of a forklift truck with a rear door.” And neither“performed any tests of such a model to see if it is both economically feasible and just as safe orsafer than the model without the door.”); Lawrence v. Raymond Corp., 501 F.App’x 515, 518–19 (6th Cir. 2012) (unpublished) (holding that because Plai ntiff’s expert only tested his door design once and did not test it on the Raymond fork lift, his test did not address the specific issues with his alternative design, “such as whether th e latching-door design [was] compatible with the Raymond forklift; th e impact a latching door would have on maintaining a Raymond forklift; or what ef fect, if any, a latc hing door would have on the forklift’s price.”).12 The district court here permissibly found Plaintiff’s expert’s testimony unreliable because on this record, we ca nnot know what impact any alternative design may have on the Raymond forklift rela ted to safety, control, performance, or price. And that is the problem. If Plai ntiff’s expert wanted to advance multiple options, so be it. But however many options he advanced, they had to be designs supported by reliable methodol ogy and capable of comparison. By not committing, Plaintiff’s expert made it impossible to compare the benefits and risks of any phantom design made of unknown materi als, attached in unknown ways, with unknown safety and performance effects, at an unknown cost, to the Raymond design. 4 And as the district court properly noted, Utah law necessarily requires a comparative analysis to dete rmine whether a safer, alte rnative design, practicable under the circumstances existed at the time of Plaintiff’s inju ry. So the district court did not abuse its discretion in excludi ng Plaintiff’s expert’s testimony. Because the district court permissibly excluded Plaintiff’s e xpert’s testimony, Plaintiff did not prove an e ssential element of his clai m—that a safer, feasible alternative design existed at the time of his injury. See Wankier v. Crown Equip.

4 Plaintiff tries to get around this issue on appeal by arguing that Raymond offers an optional spring-loaded door wh ich a consumer may add to the Raymond forklift. So, Plaintiff argues, the Raymond door exists in real life and Raymond can fit the Raymond door to the Raymond fo rklift—problem solved. And although Plaintiff may wish that it committed to the Raymond optiona l door before the district court, Plaintiff cannot rewrite history. When counsel asked Berry in a hearing whether the Raymond option d oor was his alternative desi gn, Berry responded that he would suggest a different type of door. But again, Berry did not commit to a definitive design or offer any evidence of the costs or benefits of adding that definitive design to th e Raymond forklift.13 Corp., 353 F.3d 862, 866–68 (10th Cir. 2003) (holding that under Utah law, a plaintiff must prove a safer, feasible alte rnative design). Accordingly, the district court properly granted summary judgment in Raymond’s favor.
AFFIRMED.