                              In the

    United States Court of Appeals
                For the Seventh Circuit
                    ____________________
No. 14-2018
KURT STUHLMACHER and KELLY STUHLMACHER,
                                  Plaintiffs-Appellants,

                                v.

HOME DEPOT U.S.A., INCORPORATED and TRICAM INDUSTRIES,
                                    Defendants-Appellees.
                    ____________________

         Appeal from the United States District Court for the
          Northern District of Indiana, Hammond Division.
     No. 2:10-cv-00467 — Andrew P. Rodovich, Magistrate Judge.
                    ____________________

 ARGUED NOVEMBER 4, 2014 — DECIDED DECEMBER 17, 2014
                    ____________________

   Before MANION, WILLIAMS, and SYKES, Circuit Judges.
    WILLIAMS, Circuit Judge. Kurt Stuhlmacher’s parents pur-
chased a ladder from Home Depot so that their son could
work on the roof of a cabin he was building for them. Kurt
was using the ladder for the first time when it fell, causing
him to fall. Kurt and his wife brought a personal injury ac-
tion against Home Depot and the ladder’s manufacturer,
Tricam Industries. At trial, the Stuhlmachers’ expert, Dr.
Thomas Conry, testified that the ladder was defective, likely
2                                                  No. 14-2018

causing Kurt to sense instability and involuntarily shift his
weight. The magistrate judge struck Dr. Conry’s testimony,
finding that Dr. Conry’s explanation of how the accident oc-
curred did not “square” with Kurt’s testimony that the lad-
der shot out to his left.
    Because the testimony was stricken, the Stuhlmachers
did not have any evidence showing causation, so the judge
entered judgment as a matter of law for the defendants. We
hold that the magistrate judge abused his discretion in strik-
ing Dr. Conry’s testimony. We reverse the judgment of the
district court and remand the case for a new trial.
                     I. BACKGROUND
    On November 1, 2008, Kurt Stuhlmacher, a millwright
technician, was building a cabin for his parents in Sullivan,
Indiana. Three days earlier, his parents had purchased a
four-legged fiberglass step ladder from Home Depot in or-
der for Kurt to work on the roof. Kurt, using the ladder for
the first time, had just begun to put together the rafters when
the ladder fell. He grabbed onto a rafter for a moment and
then fell on the right front rail of the ladder, striking his
groin. As a result of the fall, Kurt injured his shoulder. The
more significant injury, however, was to his penis. Doctors
later diagnosed Kurt with Peyronie’s disease, which causes
extreme pain during erection and prevents him from having
sexual intercourse.
   Several hours after the fall, Kurt looked at the ladder and
saw that it had come apart on the right rear side. The right
rear spreader bracket rivets were pulled through the right
rear rail. The ladder had been squeezed together and some
of the diagonal step braces were bent. Kurt and his wife
No. 14-2018                                                    3

Kelly brought this product liability action against Home De-
pot and Tricam Industries. The complaint alleged that the
rivets holding the support arm on one side of the ladder
failed and caused the ladder to collapse.
     The Stuhlmachers retained Dr. Conry, an accident recon-
structionist with a doctorate in mechanical engineering, to
support their claim that the subject ladder was defective and
that the defect caused Kurt’s fall. Dr. Conry prepared an ac-
cident report and was deposed by the defendants. Before tri-
al, the defendants filed a motion in limine to exclude Dr.
Conry’s testimony under Daubert v. Merrell Dow Pharmaceuti-
cals, Inc., 509 U.S. 579 (1993), which was denied. Also, in par-
tially denying the defendants’ motion for summary judg-
ment, the magistrate judge found that Dr. Conry provided
sufficient support for his theories and ruled that the plain-
tiffs could present evidence that the ladder was both defec-
tive and dangerous because the defect caused cracking and
the spreader bar to separate.
    In April 2014, the case went to trial before a jury. On the
second day of trial, Dr. Conry testified that the rivets in
Kurt’s ladder were different in two ways from the rivets
called for in the design drawings. The rivet heads were
smaller in diameter and the rivets did not have an annular
lip (that is, a lip with a series of concentric circles, allowing
for improved holding power). Dr. Conry opined that during
the manufacturing process the substituted rivets were over-
tightened, and the rivets and bracket connection permanent-
ly deformed, weakening both sides of the fiberglass of the
right rear rail. This weakened spreader bar connection, with
the rivets slicing through the fiberglass rail, dramatically
changed the integrity of the ladder. The weakened connec-
4                                                  No. 14-2018

tion would have caused Kurt to sense a change in the stiff-
ness of the ladder and involuntarily move his weight to the
left, causing the ladder to fall.
   After Dr. Conry’s direct examination, the judge excused
the jury and engaged in the following colloquy:
    Court: In your opinion, did what everybody is calling
    the spreader bar disconnect from the rail while the
    plaintiff was standing on the ladder?
    Dr. Conry: I can’t say that for sure. What I can say is
    that the stiffness of that joint where the rivets are on
    the rail was weakened substantially so that—you
    know, that the process of the rivet heads being pried
    through the material was underway while Mr.
    Stuhlmacher was on the ladder.
    Court: … What, in your opinion, caused the plaintiff
    to fall off the ladder?
    Dr. Conry: My opinion is that he sensed a change in
    the stiffness of that ladder and he was likely—
    involuntarily shifted his weight…. I think it was
    probably some kind of an involuntary motion as a re-
    sult of sensing the weakness on that side because
    once—once the crack had propagated and those rivets
    had started to pry through, that changes the structur-
    al integrity of that ladder dramatically.
    Court: In your opinion, when did the actual separa-
    tion of the spreader bar from the rail occur?
    Dr. Conry: I cannot say for sure. I know it was un-
    derway, but did it—did it happen at the point that he
    fell off? Did it happen, you know, a fraction of a sec-
No. 14-2018                                                     5

   ond after that? I can’t say. All I can say is that the ma-
   terial had that crack in it and the bracket under the
   load was prying that rivet through.
    The magistrate judge found that Dr. Conry’s testimony
regarding causation did not match up with Kurt’s testimony.
The judge said, “[t]he plaintiff never testified that the ladder
became unstable, that the ladder in any way shook. His tes-
timony was that all the sudden the ladder went to the left.”
The judge reasoned that even if the ladder was defective in
the way Dr. Conry opined, the plaintiffs had failed to show a
causal link between the alleged defect and the accident, since
Dr. Conry’s testimony could not be reconciled with Kurt’s
testimony.
   At the request of the defendants, the judge struck Dr.
Conry’s testimony. With that evidence gone, the plaintiffs
admitted that they had no evidence to establish proximate
cause and the judge entered judgment as a matter of law for
the defendants. The Stuhlmachers appeal.
                        II. ANALYSIS
    The Stuhlmachers argue that the magistrate judge im-
properly excluded Dr. Conry’s testimony and invaded the
province of the jury when he found that Kurt’s testimony
was not reconcilable with Dr. Conry’s explanation of causa-
tion. This incorrect evidentiary ruling resulted in the judge
erroneously entering judgment as a matter of law for the de-
fendants. We review evidentiary decisions, including deci-
sions whether to admit expert testimony, for an abuse of dis-
cretion. Walker v. Soo Line R.R. Co., 208 F.3d 581, 586 (7th Cir.
2000). For expert testimony, we review de novo whether the
district court properly applied the Daubert framework. Id. at
6                                                    No. 14-2018

590. If properly applied, then we review the ultimate deci-
sion of whether to admit the testimony for abuse of discre-
tion. Id. And we review the grant of judgment as a matter of
law de novo. Hossack v. Floor Covering Assocs. of Joliet, Inc.,
492 F.3d 853, 859 (7th Cir. 2007). The plaintiffs do not argue
that the judge improperly applied the Daubert framework, so
we limit our analysis to an abuse of discretion review of the
ultimate decision to strike Dr. Conry’s testimony.
    Expert testimony is admissible at trial if the testimony is
relevant to a fact in issue, is based on sufficient facts or data,
and is the product of reliable scientific or other expert meth-
ods that are properly applied. Fed. R. Evid. 702. The Su-
preme Court in Daubert interpreted Rule 702 to require that
district courts, prior to admitting expert testimony, deter-
mine whether the testimony is reliable and whether it will
assist the trier of fact in determining some fact that is at is-
sue. 509 U.S. at 589. That is, the district court serves as a
“gatekeeper” whose role is to ensure that an expert’s testi-
mony is reliable and relevant. Smith v. Ford Motor Co., 215
F.3d 713, 718 (7th Cir. 2000).
    Here, the magistrate judge found that Dr. Conry’s testi-
mony was reliable enough to be heard by the jury. However,
after Dr. Conry’s direct examination, the judge struck his tes-
timony as irrelevant under Daubert because he found that
Dr. Conry’s version and Kurt’s version did not square. In the
magistrate judge’s view, Dr. Conry testified to one fact pat-
tern of how the accident occurred, and Kurt testified to an-
other fact pattern. We do not agree. Dr. Conry’s and Kurt’s
testimony are easily reconcilable, particularly since the fall
happened so quickly.
No. 14-2018                                                   7

    An expert’s testimony qualifies as relevant under Rule
702 so long as it assists the jury in determining any fact at
issue in the case. Smith, 215 F.3d at 718. Experts are allowed
to posit alternate models to explain their conclusions. Walker,
208 F.3d at 587. “Where an expert’s hypothetical explanation
of the possible or probable causes of an event would aid the
jury in its deliberations, that testimony satisfies Daubert’s
relevancy requirement.” Smith, 215 F.3d at 718–19. The ques-
tion of whether the expert’s theory is correct given the cir-
cumstances of a particular case is a factual one left for the
jury to determine. Id. at 719.
    Here, the judge took that question away from the jury. A
jury could have found that Dr. Conry’s theory of the acci-
dent was credible and that Kurt’s testimony merely reflected
his memory of the event as it was happening. See Lauzon v.
Senco Prods., 270 F.3d 681, 695 (8th Cir. 2001) (reversing the
district court’s exclusion of the expert’s testimony because,
although the expert’s opinion and the plaintiff’s account of
events were seemingly varied, there was a “sufficient nexus”
between the two testimonies and the expert testimony
would aid the jury in their final determination). It is under-
standable that Kurt would not recall exactly what happened.
Kurt testified that he was standing on the seventh step of the
ladder when “it just, like, fell out–fell this way out from un-
derneath me to the left.” He did not see the ladder as it fell,
since he grabbed onto the rafter to stop his fall. So he did not
know whether the ladder split right before or right after he
fell. Furthermore, regardless of when the ladder came apart,
the jury would be entitled to find that the manufacturing de-
fect Dr. Conry described caused Kurt’s accident if it caused
him to lose his balance.
8                                                    No. 14-2018

    Dr. Conry testified that Kurt likely would have involun-
tarily moved as a result of sensing a change in the stiffness of
the ladder. Kurt’s statement that the ladder suddenly moved
to the left could have been the sensed stiffness change or in-
stability that Dr. Conry described. The magistrate judge
faulted Kurt for not testifying that the ladder felt unstable
before its fall, but Kurt also did not testify that he felt unsta-
ble or lost his balance. Obviously, for the fall to have oc-
curred, something or someone had to have been unstable.
From Dr. Conry’s and Kurt’s testimony, the jury could
choose to infer that the weakened connection between the
spreader bar and the rail caused the ladder to become unsta-
ble, making Kurt involuntarily move. Dr. Conry’s testimony
would have assisted the jury in determining what caused the
ladder to move.
    Kurt’s fall happened very quickly. He testified that he
did not see or hear anything, but that the ladder suddenly
moved to his left. His expert then reconstructed what hap-
pened and gave his opinion on how an alleged defect could
have caused the accident. It is not the trial judge’s job to de-
termine whether the expert’s opinion is correct. Smith, 215
F.3d at 719. Instead, under the relevancy prong, the judge is
limited to determining whether expert testimony is pertinent
to an issue in the case. Id. Here, the judge improperly ex-
panded his role beyond gatekeeper to trier of fact. See Lau-
zon, 270 F.3d at 694 (holding that under the relevancy prong
of Daubert, the opinion offered by an expert is admissible
where it is “sufficiently related to the facts of the case such
that it will aid the jury in resolving the factual dispute”); see
also Lee v. Smith & Wesson Corp., 760 F.3d 523, 526 (6th Cir.
2014) (reversing the district court’s exclusion of the expert’s
testimony and stating that a party may prove his case by any
No. 14-2018                                              9

relevant evidence, even though that evidence may contradict
the testimony of a witness previously called by him).
    For these reasons, we conclude that the magistrate
judge’s decision striking Dr. Conry’s testimony cannot
stand.
                   III. CONCLUSION
    The judgment of the district court is REVERSED and this
case is REMANDED for further proceedings consistent with
this opinion.
