[DO NOT PUBLISH]

In the

United States Court of Appeals

For the Eleventh Circuit

____________________

No. 23-10050

____________________

AUSTIN J. RAPPUHN, 

Plaintiff-Appellant,

versus

PRIMAL VANTAGE COMPANY, INC., 

Defendant- Appellee,

____________________

Appeal from the United States District Court

for the Southern District of Alabama

D.C. Docket No. 1:20-cv-00528-CG-N

____________________

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2 Opinion of the Court 23-10050

Before WILLIAM PRYOR, Chief Judge, and JORDAN and BRASHER, Circuit Judges.

PER CURIAM:

This appeal requires us to decide whether the district court 

abused its discretion when it limited the opinions of two of Austin 

Rappuhn’s expert witnesses and whether it erroneously granted 

summary judgment to Primal Vantage Company, Inc. The district 

court granted summary judgment by saying that there was no genuine dispute of material fact as to the alleged violation of the Alabama Extended Manufacturer’s Liability Doctrine, negligence, and 

wantonness after excluding key portions of the experts’ testimony. 

But the district court misunderstood the experts’ testimony and 

weighed its persuasiveness in determining its admissibility, which 

are not valid bases for excluding expert testimony. The district 

court didn’t perform a proper expert analysis under Daubertv. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579 (1993), and this error infected the summary judgment decision. The district court also incorrectly reasoned that the possibility of user error with an alternative design means that Rappuhn must lose. We reverse the district 

court’s grant of summary judgment and its expert testimony exclusions and remand for further proceedings consistent with this opinion.

I.

Austin Rappuhn went on a deer hunting trip with his father 

in November 2018. Rappuhn brought a tree stand—the PVCS-400, 

which was designed, manufactured, produced, and distributed by 

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Primal Vantage. The PVCS-400 is a climbing tree stand: a hunter 

uses the tree stand to scale up the trunk of a tree until he reaches 

the height from which he wishes to hunt. The PVCS-400 has a seat 

and a foot platform, which are secured to the tree with cables that 

wrap around the trunk and attach to the tree stand with fasteners 

called Quickclips. A Quickclip is an open-ended latch that fits over 

an open-ended pin.

Rappuhn and his father split up and each found a tree from 

which to hunt. Rappuhn set up his PVCS-400, which he had done 

several times before, and began to climb a tree. As he was scaling 

the tree, he heard a popping sound and felt something break free. 

He fell to the ground from a height of around seven feet. Rappuhn 

lost consciousness when he fell; and upon regaining consciousness, 

he found himself face down in the mud, with the seat platform of 

the PVCS-400 wrapped around him. He couldn’t move and called 

for his father’s help. When his father got to him, he called 911. His 

father noticed that the foot platform of the PVCS-400 was still attached to the tree. He also found one of the Quickclips on the 

ground nearby and saw that the top platform’s securement cable 

had come out of the frame on the right side of the tree stand. Rappuhn went to the hospital, where he learned that he was permanently paralyzed from the chest down.

Rappuhn sued Primal Vantage in federal court and alleged a 

violation of the Alabama Extended Manufacturer’s Liability Doctrine, negligence, and wantonness. He alleges that the PVCS-400’s 

Quickclip disengaged while he was climbing the tree and that 

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Primal Vantage should have used a safer way to secure the cables 

that hold the tree stand to the tree. To support this theory, Rappuhn presented the testimony of two expert witnesses: Guy 

Avellon, a fastener expert, and Dr. Jahan Rasty, a mechanical engineering expert.

Avellon, as an expert on fasteners, investigated the different 

design options for tree stand fasteners and their relative safety and 

utility. Avellon opined in a report that the Quickclip is a relatively

unsafe fastener choice for a tree stand because the pin is too long 

and not tight to the frame, the stiffness of the latch spring is variable, and the open-ended design makes the Quickclip capable of disengaging. Avellon opined in a report that safer fastener designs like 

a nut-and-bolt design were feasible, practical, and readily available 

when the PVCS-400 was manufactured and sold. Avellon explained 

that these alternative designs are safer because they have a tighter 

fit than a Quickclip; do not have an open-ended design that can 

cause false-latch scenarios; and must be screwed in, preventing unexpected disengagement while in use. Avellon’s expert report also

explained that “[a]s designed, there are no mechanical means or 

warnings provided to assure the Quick Clip is properly fastened before a user begins to ascend a tree.” And it similarly stated that 

there are not “physical means” to ensure the cable is “locked in position.” Later, in his deposition testimony, Avellon testified that a 

user could “visually” detect whether a Quickclip was “properly 

closed” by looking at it.

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Rasty, as an expert on mechanical engineering, investigated

what may have caused the PVCS-400 to detach from the tree for 

Rappuhn to have fallen. Rasty concluded in a report that the tree 

stand most likely detached because a Quickclip disengaged under a 

false-latch scenario. Rasty explained that a Quickclip may appear 

fastened when it is not and thus can disengage when the tree 

stand’s user is climbing the tree. Rasty performed tests to evaluate 

this theory. Although he didn’t perform any tests with a heavy load

on the tree stand, he explained that the presence of a heavy load on 

the tree stand wouldn’t change his test results or conclusion. Specifically, he said that any load would be perpendicular to the force 

he was testing and would make a minimal difference in the likelihood of the tree stand coming unlatched.

Primal Vantage moved to exclude or limit these experts’ testimony and for summary judgment. The district court agreed with 

Primal Vantage and decided that it would not consider Avellon’s 

opinion about whether a Quickclip allows a user to confirm that it 

is closed or Rasty’s opinion about the force it takes to disengage a 

Quickclip. The district court ruled that Avellon’s opinion that the 

tree stand was defective should not be allowed because of inconsistencies in his testimony. The district court explained that 

Avellon “opined [in his report] that the tree stand was defectively 

designed because there was no way to verify if the Quickclip was 

properly fastened before a user begins to ascend a tree” but had 

contradicted himself in his deposition by testifying that a user can 

tell whether a Quickclip is properly installed by looking at it or feeling if it is properly closed. The district court excluded Rasty’s 

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causation opinion because, unlike Rasty, Primal Vantage’s expert 

testified that a load would make a difference in the force it would 

take to release a Quickclip. The district court also discounted 

Rasty’s testimony by saying it contradicted Rappuhn’s testimony 

that he had checked that the tree stand was latched before he began 

climbing.

After excluding this proposed expert testimony, the district 

court granted summary judgment for Primal Vantage, concluding 

there was no genuine dispute of material fact. The district court 

based its conclusion on the idea that, without expert testimony,

Rappuhn could not establish that his injuries would have been 

eliminated or reduced with an alternative design. The district court 

also concluded that Rappuhn’s proposed alternative design was insufficient to meet his burden because it was susceptible to user error. Rappuhn appealed.

II.

We review a district court’s exclusion of expert testimony 

for an abuse of discretion. See Rink v. Cheminova, Inc., 400 F.3d 1286, 

1291 (11th Cir. 2005) (citing Kumho Tire Co. v. Carmichael, 526 U.S. 

137, 152 (1999)). “A district court abuses its discretion if it applies 

an incorrect legal standard, follows improper procedures in making 

the determination, or makes findings of fact that are clearly erroneous.” Klay v. United Healthgroup, Inc., 376 F.3d 1092, 1096 (11th 

Cir. 2004) (quoting Martin v. Automobili Lamborghini Exclusive, Inc., 

307 F.3d 1332, 1336 (11th Cir. 2002)). When reviewing a district 

court’s ruling on the admission of expert testimony, “we defer to 

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the district court’s ruling unless it is manifestly erroneous.” Rink, 

400 F.3d at 1291 (cleaned up).

We review summary judgment rulings de novo, “applying 

the same legal standards that bound the district court.” Seamon v. 

Remington Arms Co., 813 F.3d 983, 987 (11th Cir. 2016) (citing Nat’l 

Fire Ins. Co. of Hartford v. Fortune Constr. Co., 320 F.3d 1260, 1267 

(11th Cir. 2003)). “Motions for summary judgment should be 

granted only when the pleadings, depositions, answers to interrogatories, and admissions on file, together with the affidavits, show 

that there is no genuine issue as to any material fact and that the 

moving party is entitled to judgment as a matter of law.” Id. at 987–

88 (citing Fed. R. Civ. P. 56(c); Celotex Corp. v. Catrett, 477 U.S. 317, 

322 (1986)).

III.

Rappuhn argues that the district court applied an incorrect 

legal standard in excluding portions of the experts’ testimony and 

that this error infected its summary judgment decision. We agree. 

We address these two issues in turn.

A.

We will start with the district court’s decision to disregard 

Avellon’s and Rasty’s testimony. Federal Rule of Evidence 702 governs the admissibility of expert testimony. An expert witness may 

testify 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 

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sufficient facts or data”; (c) “the testimony is the product of reliable 

principles and methods”; and (d) the expert reliably applied the 

principles and methods to the case’s facts. Fed. R. Evid. 702. Under 

Rule 702, district courts play a “gatekeeping” role in the admission 

of expert testimony. Daubert, 509 U.S. at 597. District courts must 

consider whether “the expert is qualified to testify competently”

about the matter he intends to address, whether “the methodology 

by which the expert reaches his conclusions is sufficiently reliable,”

and whether “the testimony assists the trier of fact . . . to understand the evidence or to determine a fact in issue.” City of Tuscaloosa 

v. Harcros Chems., Inc., 158 F.3d 548, 562 (11th Cir. 1998). To evaluate reliability, a district court applies the Daubert standard, considering (1) “whether the expert’s theory can be and has been tested,”

(2) “whether the theory has been subjected to peer review and publication,” (3) “the known or potential rate of error of the particular 

scientific technique,” and (4) “whether the technique is generally 

accepted in the scientific community.” McCorvey v. Baxter 

Healthcare Corp., 298 F.3d 1253, 1256 (11th Cir. 2002) (citing Daubert, 509 U.S. at 593–94).

Although the basis for the district court’s evidentiary rulings 

is not clear, we believe the district court concluded that Rappuhn’s 

proposed expert testimony was unreliable under Daubert. The district court did not cite Federal Rule of Evidence 702, Daubert, or 

any of our case law laying out the standard for expert testimony 

admissibility. But the district court’s reasoning tracks most closely 

with an assessment of reliability. The district court did not, for example, suggest that either Avellon or Rasty was unqualified as an 

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expert; nor did the district court question whether Avellon’s or 

Rasty’s testimony would be useful for the jury. Accordingly, we 

will evaluate the district court’s reasoning as concerning the reliability of Avellon’s and Rasty’s proposed expert testimony.

We’ll turn first to Avellon. The district court excluded 

Avellon’s design testimony because of ostensibly conflicting statements in his testimony and expert report. The district court explained that Avellon “opined [in his report] that the tree stand was 

defectively designed because there was no way to verify if the 

Quickclip was properly fastened before a user begins to ascend a 

tree.” But, according to the district court, Avellon contradicted 

himself during his deposition when he testified that a user can tell 

whether a Quickclip is properly installed by looking at it or feeling 

if it is properly closed. Because Avellon’s testimony was purportedly contrary to his report, the district court ruled that Avellon’s 

opinion that the tree stand was defective should not be allowed.

The district court was wrong to exclude this testimony for 

two reasons.

First, Avellon’s statements are not, in fact, inconsistent. During his deposition, Avellon testified that a user could “visually” detect whether a Quickclip was “properly closed” by looking at it. But 

Avellon’s expert report says that “[a]s designed, there are no mechanical means or warnings provided to assure the Quick Clip is 

properly fastened before a user begins to ascend a tree.” Avellon’s 

statement that a user could look at a Quickclip and determine it is 

“properly closed” (in the sense that the loop is fully around the rod) 

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does not conflict with his statement that the Quickclip doesn’t feature any type of physical means to ensure it is “locked in position” 

or a mechanical means or warning to know that it is not “properly 

fastened” (in the sense of being fully engaged and unable to pop 

open). We have previously held that a district court manifestly 

erred when it mischaracterized an expert’s opinion. Seamon, 813 

F.3d at 991. That error occurred here too.

Second, even if there were some kind of inconsistency between the report and deposition testimony, we could not say that 

it undermines the admissibility of Avellon’s testimony. The inquiry

under Daubert is not whether the expert’s assessment is incontrovertible. “Daubert does not require that a party who proffers expert 

testimony carry the burden of proving to the judge that the expert’s 

assessment of the situation is correct.” Ruiz-Troche v. Pepsi Cola of 

Puerto Rico Bottling Co., 161 F.3d 77, 85 (1st Cir. 1998). The reliability 

inquiry is about the principles and methods the expert used, not 

whether the expert has provided credible testimony. See Fed. R. 

Evid. 702; Daubert, 509 U.S. at 590; McCorvey, 298 F.3d at 1256. Instead of excluding an expert’s testimony entirely, “[v]igorous crossexamination, presentation of contrary evidence, and careful instruction on the burden of proof” remain the preferred “means of 

attacking shaky but admissible evidence.” Daubert, 509 U.S. at 596.

Even if a jury could find some inconsistency between Avellon’s report and his deposition that might undermine his testimony at trial, 

that credibility question is one for the jury to answer.

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The district court made the same kind of errors in its assessment of Rasty’s testimony. The district court excluded Rasty’s causation testimony in part because Primal Vantage’s expert testified 

that a user weight load would make a difference in the force it 

would take to release a Quickclip, meaning—in the district court’s 

view—Rasty’s opinion was not credible because he didn’t perform 

his test on the tree stand with a user weight load. Based on these 

findings, the district court concluded that Rasty’s testimony was 

unreliable.

This analysis—crediting one expert over another—misapplies Daubert and intrudes on the province of the jury. We have 

held that “a district court may not exclude an expert because it believes one expert is more persuasive than another expert.” Rink, 

400 F.3d at 1293 n.7. In opposition to the view of the defendant’s 

expert, Rasty explained in his deposition why testing with a user 

weight load didn’t matter and wouldn’t have changed his opinion.

The comparison of the testing done by Rasty and the defendant’s

expert goes to credibility, not reliability. As we’ve explained, “objections to the inadequacies of a study are more appropriately considered” as “going to the weight of the evidence rather than its admissibility.” Rosenfeld v. Oceania Cruises, Inc., 654 F.3d 1190, 1193 

(11th Cir. 2011) (quoting Hemmings v. Tidyman’s Inc., 285 F.3d 1174, 

1188 (9th Cir. 2002)) (citing Quiet Tech. DC-8, Inc. v. Hurel-Dubois UK 

Ltd., 326 F.3d 1333, 1345 (11th Cir. 2003)). Typically, the “failure to 

include variables” in an expert’s testing “will affect the analysis’[s] 

probativeness, not its admissibility.” Quiet Tech. DC-8, Inc., 326 F.3d 

at 1346 (quoting Bazemore v. Friday, 478 U.S. 385, 400 (1986)).

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The district court committed the same error when it discounted the weight of Rasty’s testimony on the ground that it contradicted Rappuhn’s testimony that the tree stand was latched

when he started climbing. There may, or may not, be some inconsistency between Rappuhn’s recollection of what he saw and what 

Rasty believes caused the accident. But a district court cannot limit 

an expert’s testimony or grant summary judgment by crediting one 

witness over another.

In failing to follow well-established law, the district court 

abused its discretion. As we have explained, “[t]o faithfully discharge its gatekeeping duty,” the district court “must engage in a 

rigorous” analysis. United States v. Barton, 909 F.3d 1323, 1331 (11th 

Cir. 2018). We cannot say that the district court’s reasons for excluding this expert testimony reflects rigorous analysis. Neither 

Avellon’s nor Rasty’s testimony should have been excluded for the 

reasons the district court gave.

B.

We’ll turn now to the district court’s summary judgment 

decision. The district court concluded that there was no genuine 

dispute of material fact as to defective design and causation, which 

led to summary judgment on the Alabama Extended Manufacturer’s Liability Doctrine, negligence, and wantonness claims. Rappuhn argues that the district court’s summary judgment decision 

was erroneous in several respects. We will address two.

First, the district court’s summary judgment was based on 

its decision to exclude the expert testimony that would have 

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created a genuine dispute of material fact. We need not perform 

the full summary judgment analysis ourselves. It is enough to say 

that the summary judgment was in error because it was based on 

the district court’s abuse of discretion in excluding this testimony.

Second, we agree with Rappuhn that the district court also 

erred in analyzing his proposed alternative design. The district 

court suggested that, even if there were substantial evidence of causation, Rappuhn cannot establish that his injuries would have been 

eliminated or reduced with an alternative design unless that alternative design is resistant to all user error. The district court was 

incorrect. To prove a safer alternative design under Alabama law, 

a plaintiff must establish that (1) his injuries would have been eliminated or in some way reduced by the alternative design and (2) the 

utility of the alternative design outweighed the utility of the design 

actually used. See Hosford v. BRK Brands, Inc., 223 So. 3d 199, 203 

(Ala. 2016). One way Rappuhn could meet his burden under the 

first element is by establishing that an alternative design—such as 

his proposed nut-and-bolt design—has a lower risk of user error and 

device failure such that his injury wouldn’t have occurred if it had 

been used. See Gen. Motors Corp. v. Edwards, 482 So. 2d 1176, 1189 

(Ala. 1985) (“The critical question is whether, under all of the surrounding circumstances, a manufacturer has created an unreasonable risk of increasing the harm in the event of the statistically inevitable collision.” (quoting Curtis v. Gen. Motors Corp., 649 F.2d 

808, 812 (10th Cir. 1981))), overruled on other grounds by Schwartz v. 

Volvo N. Am. Corp., 554 So. 2d 927 (Ala. 1989), as recognized in Haddan v. Norfolk S. Ry. Co., 367 So. 3d 1067 (Ala. 2022).

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IV.

We REVERSE and REMAND for further proceedings consistent with this opinion.

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