Chad Darwin Koetz, Trustee for the Heirs and Next-of-Kin of Gloria Lynn Koetz, Appellant,

This opinion is nonprecedential except as provided by
Minn. R. Civ. App. P. 136.01, subd. 1(c).

STATE OF MINNESOTA
IN COURT OF APPEALS
A25-0480

Chad Darwin Koetz, Trustee for the Heirs
and Next-of-Kin of Gloria Lynn Koetz,
Appellant,

vs.

Mayo Clinic,
Respondent.

Filed September 8, 2025
Affirmed
Connolly, Judge

Olmsted County District Court
File No. 55-CV-22-5358

Elham B. Haddon, Sandberg Haddon Law Firm, Rochester, Minnesota (for appellant)

Andrew Brantin gham, Samuel Audley, Brock Huebner, Dorsey & Whitney LLP,
Minneapolis, Minnesota; and

Matthew J. Hanzel, Mayo Clinic Legal Department, Rochester, Minnesota (for respondent)

Considered and decided by Connolly, Presiding Judge; Schmidt, Judge; and Harris,
Judge.
NONPRECEDENTIAL OPINION
CONNOLLY, Judge

Appellant, trustee for the next-of-kin of a deceased patient of respondent, a medical-
care provider, challenges the denial of appellant’s motion for a new trial, arguing that the
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district court erred in excluding some of appellant’s expert -witnesses’ testimony and in
granting respondent’s motion for judgment as a matter of law (JMOL). We affirm.
FACTS
On June 29, 2020, Gloria Koetz (Koetz) had surgery to amputate her right leg below
the knee at respondent Mayo Clinic (Mayo). There were no complications. On June 30,
Mayo staff noted that Koetz was doing well and adjust ed her pain medication to further
reduce her post-operative pain. Early on July 1, 2020, Mayo staff noted that Koetz was in
no acute distress and made further adjustments to her pain medication.
Around 10:30 a.m. on July 1, Mayo staff found Koetz gasping and unresponsive,
agitated, and possibly hallucinating. Mayo staff assume d this was a reaction to her pain
medication, discontinued some medication, and called a Rapid Response Team. Both the
physician assistant who led the Rapid Response Team and a critical -care physician
suspected that serotonin syndrome was a potential cause of the change in Koetz’s status.1
Koetz was transferred to an intensive care unit (ICU) and remained unresponsive and

1Serotonin is defined as “[a] vasoconstrictor, liberated by platelets; inhibits gastric
secretion and stimulates smooth muscle; also acts as a neurotransmitter; present in the
central nervous system, many peripheral tissues and cells, and carcinoid tumors. ”
Stedman’s Medical Dictionary for the Health Professions and Nursing Illustrated, 7th ed.,
Wolters Kluwer Health, 2012, 1527. The definition makes no reference to intracranial
hemorrhage, given as the cause of Koetz’s death. The report of one of Mayo’s expert
witnesses, Dr. J.L., a vice chief of critical care at the Massachusetts General Hospital and
an associate professor at the Harvard Medical School, indicated that he “was expected to
explain that there is no diagnostic test to identify serotonin syndrome” and “to testify that
the appropriate treatment is to withdraw serotonergic medications, provide supportive care,
and observe the patient as they recover.”

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agitated. Another critical-care physician also suspect ed serotonin syndrome was a cause
of Koetz’s condition and halted her serotonergic medications.
The chair of Mayo’s Division of Hospital Neurology and Neurocritical Care, who
was a board-certified neurologist, (the neurologist) then assessed Koetz and confirmed both
the view that serotonin was the best explanation of her condition and the decision to
withdraw serotonergic medication.
On the morning of July 2, 2020, Koetz was less responsive and there w ere
significant changes from her July 1 presentation. A computed tomography (CT) scan of
her brain was performed and reviewed by the neurologist. He found it revealed “a massive
left hemispheric acute brain hemorrhage” and that, since his examination of Koetz on July
1, she had “suffered an unsurvivable brain hemorrhage” from “a ruptured aneurism with
bleeding infiltrating into the parenchyma and causing the massive swelling.” A Mayo
neurosurgeon confirmed this finding and Koetz died on July 3. The cause of her death was
given as intraparenchymal and subarachnoid intracranial hemorrhage with a ruptured
arterial aneurism.
In July 2022, appellant Chad Darwin Koetz (appellant), the trustee for Koetz’s next-
of-kin, brought this action against Mayo , alleging that its negligent medical care caused
Koetz’s death. On September 13, 2022, appellant agreed to provide all expert disclosures
by March 13, 2023, 2 and both parties agreed to complete factual discovery by September

2See Minn. Stat § 145.682, subds. 2, 4 (2022) (requiring service of expert disclosures within
180 days after commencement of discovery); see also Minn. R. Civ. P. 26.01(b).
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1, 2023. On February 28, 2023, an amended scheduling order gave May 3, 2024, as the
pretrial hearing date and May 13, 2024, as the start of a date-certain trial.
On July 12, 2022, appellant disclosed one expert, Dr. J.G., a research neurologist,
whose report expressed the opinions that Mayo failed to timely identify, diagnose, and treat
Koetz’s serotonin syndrome, causing her death, and that Koetz’s brain aneurism was a
result of the serotonin syndrome, which started the chain of events leading to her death.
On May 12, 2023, Mayo disclosed four expert witnesses whose reports refuted Dr. J.G.’s
opinions; they stated that Mayo acted properly and that there was no cau sal relationship
between Koetz’s serotonin syndrome and her intracranial hemorrhage.
Mayo also stated that it would object to any additional claims and theories offered
by appellant in the future. On December 4, 2023, the district court ordered that Dr. J.G.’s
deposition be completed by April 15, 2024, to comply with the date-certain trial schedule
requirement.
On January 30, 2024 , over nine months after the deadline for disclosure of
appellant’s expert witnesses and less than four months before trial, appellant identified two
additional expert witnesses, one a neurosurgeon and the other an internal -medicine and
critical-care specialist. Unlike the opinion of Dr. J.G., which alleged a causal relationship
between Koetz’s serotonin syndrome and her intrac ranial hemorrhage, their opinions
concerned Mayo’s alleged failure to manage Koetz’s blood pressure and her intracranial
bleeding. Mayo moved to exclude the untimely disclosed witnesses, and in March 2024,
the district court granted Mayo’s motion.
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During the trial, Mayo asked the district court to preclude Dr. J.G. from testifying
as to a causal connection between serotonin syndrome and intracranial hemorrhage on the
ground of lack of foundation. The district court decide d to question Dr . J.G. outside the
presence of the jury on the alleged causal connection. Dr. J.G. testified that nine medical
articles support ed the causal connection , but he was unable to specifically identify any
article that actually did this and ultimately admitted that there was no medical support for
the causal link he alleged. The district court therefore limit ed Dr. J.G.’s testimony to
exclude the view that Koetz’s “massive hea d bleed [was] caused by the serotonin
syndrome.” Dr. J.G. testified in accord with the district court’s decision.
On May 15, 2024, after testimony from some other witnesses, appellant rested his
case. Mayo then moved for JMOL. Following breaks to review arguments and the
relevant law, the district court granted Mayo’s motion. On May 29, 2024, the district court
filed an Order for Judgment dismissing appellant’s claims with prejudice. On July 3, 2024,
appellant moved for a new trial or for relief from judgment. Following a November 4,
2024, hearing on the motion , the district court on January 23, 2025 , denied appellant’s
motion.
Appellant challenges the denial of the motion, arguing that the district court abused
its discretion in excluding appellant’s untimely disclosed expert witnesses and erred in
granting Mayo’s motion for JMOL.3

3 On appeal, a ppellant concedes that, unless the district court abused its discretion in
excluding Dr. J.G.’s testimony on the alleged causal relationship between Koetz’s
serotonin syndrome and her intracranial hemorrhage, appellant could not have proved
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DECISION
1. Exclusion of Appellant’s Untimely Disclosed Expert Witnesses
At the hearing on Mayo’s motion to exclude the untimely disclosed witnesses, t he
district court stated:
[P]ursuant to [Minn. Stat. § 145.682 (2024)], the court is going
to exclude the untimely disclosed expert opinions. These are
deadlines that both parties agreed to, and these reports were
disclosed well after these deadlines, and there has been no
justification to support that this was done inadvertently. In
fact, quite to the contrary. . . . [T] he initial disclosure [date]
was March 1 3th of 2023, so their disclosures are 10 months
after that. They are two months after the close of the fact
discovery. Even if the Court were to characterize [the untimely
disclosed witnesses’ reports] as rebuttal reports, which I’m not
sure [they are], . . . they’re not timely as rebuttal reports. [4]
As far as the prejudice to Mayo on whether . . . they
have demonstrated that there is prejudice, I don’t know that
that’s their obligation, but I don’t see any way for the Court to
allow these reports and still keep the May [13, 2024,] trial date.
So I do find there would be prejudice here, in addition to the
fact that these reports, they do seem to indicate a completely
different--a change in sort of theory of the case, yet we’re
relying on the same medical records, which [the] parties had
well in advance to even proceeding with the case or . . .
creating these deadlines. . . . So the Court is going to exclude
the most recently disclosed experts being that they are untimely
[disclosed], and it would result in prejudice to [Mayo], and that
there is no justification or excusable neglect that the Court has
found in the arguments before the Court.

Mayo’s negligence to a jury , so the granting of Mayo’s motion for JMOL was
“preordained.”
4 Appellant characterizes his untimely disclosed witnesses as rebuttal witnesses, but even
if this were true, their disclosure was untimely. The disclosure of “evidence . . . intended
solely to contradict or rebut evidence on the same subject matter identified by another party
. . . must be made “within 30 days after the other party’s disclosure.” Minn. R. Civ. P
26.01(b)(4)(B). Mayo disclosed its experts on May 12, 2023, and appellant did not disclose
his alleged rebuttal expert witnesses until January 30, 2024.
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(Footnote added).

The district court later issued a written order granting Mayo’s motion, stating that
appellant “ha[d] not demonstrated good cause, excusable neglect, or other justification for
the failure to timely disclose these expert witnesses,” and that Mayo “would be prejudiced
by allowing the newly disclos ed experts to testify at trial due to a change in the theory of
[appellant’s] case provided by these experts’ testimony.”
This court reviews a decision to exclude untimely disclosed expert witnesses for an
abuse of discretion. See, e.g., Anderson v. Rengachary, 608 N.W.2d 843, 848 -50 (Minn.
2000) (concluding that the district court did not abuse its discretion by dismissing the
plaintiff’s claim after the 180 -day deadline to submit an affidavit of expert identification
expired); see also Mercer v. Andersen, 715 N.W.2d 114, 123 (Minn. App. 2006) (providing
that the discretion is subject to the requirements of Minn. Stat. § 145 .682, which “is
unambiguous and requires strict compliance with its provisions”).
The court shall include in a scheduling order a deadline prior to
the close of discovery for all parties to answer expert
interrogatories for all experts to be called at trial. No additional
experts may be called by any party without agreement of the
parties or by leave of the court for good cause shown.

Minn. Stat. § 145.682, subd. 4(c) . Mayo opposed the untimely disclosed experts whom
appellant wanted to call, and appellant did not ask the district court for leave to show good
cause. A plaintiff’s failure to request or move for an extension of time to satisfy the
statutory requirement has been held to justify dismissal of his claims. See, e.g., Maloney
v. Fairview Cmty. Hosp ., 451 N.W.2d 237, 240 (Minn. App. 1990) , rev. denied (Minn.
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Mar. 22, 1990). Thus, appellant had neither the “agreement of the parties” nor “leave of
the court for good cause shown.”
A district court may grant an extension of the statutory deadline only if the plaintiff’s
“failure to act resulted from excusable neglect.” Mercer, 715 N.W.2d at 123. A finding
of excusable neglect requires that a plaintiff (1) have a reasonable claim on the merits, (2)
have a reasonable excuse for failure to comply with the statutory time limit, (3) have acted
with due diligence after receiving notice of the time limit, and (4) that the grant of the
extension of the deadline will not result in any substa ntial prejudice to the defendant.
Anderson, 608 N.W.2d at 850.
As to (1), appellant’s expert witness Dr. J.G., when questioned by the district court,
was unable to provide any scientific foundation for his theory of the case: that Koetz’s
serotonin syndrome caused her intracranial hemorrhage. Thus, the district court did not
abuse its discretion in determining that appellant did not have a reasonable claim on the
merits.
As to (2), appellant argues that he could not identify experts willing to commit to a
May trial any earlier and that the failure to timely disclose was his attorney’s fault. But
not all mistakes, whether of fact or of law, and whether
committed by a party to an action or by his attorney, are subject
to relief. . . . [T]he district court is in the best position to
evaluate the reasonableness of the excuse, the prejudice to the
other party, and whether the party has a reasonable claim or
defense. . . . [T]he decision is fact intensive.

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Cole v. Wutzke, 844 N.W.2d 634, 638 (Minn. 2016) (quotations and citations omitted). The
district court did not abuse its discretion in concluding that appellant did not have a
reasonable excuse for failure to comply with the time limit.
As to (3), appellant had agreed to the dates for disclosure of expert witnesses, and
he timely disclosed Dr. J.G. as his expert witness; thus, appellant knew of the disclosure
deadline and did not need further notice of the time limit.
As to (4), the district court noted in its March 25, 2024, order that Mayo “would be
prejudiced by allowing the newly disclosed experts to testify at trial due to a change in the
theory of [appellant’s] case provided by these experts’ testimony.” Thus, appellant did not
show any of the components of excusable neglect without which the district court could
not extend the deadline, and the district court did not abuse its discretion in not extending
the deadline. See Mercer, 715 N.W.2d at 123.
Appellant’s reply to Mayo’s motion to exclude the untimely -disclosed expert
witnesses’ testimony does not deal with excusable neglect. Instead, it relies on four cases
that do not refer to Minn. Stat. § 145.682: Dennie v. Metropolitan Med. Ctr., 387 N.W.2d
401 (Minn. 1986); Cornfeldt v. Tongen , 262 N.W.2d 684 (Minn. 1977); Kraushaar v.
Austin Med. Clinic, P.A., 393 N.W.2d 217 (Minn. App. 1986), rev. denied (Minn. Nov. 19,
1986); and Riewe v. Arnesen, 381 N.W.2d 448 (Minn. App. 1986), rev. denied (Minn. Mar.
22, 1986). He cites these cases to argue that the district court abused its discretion by not
applying a less severe sanction for untimely disclosure of witnesses than the exclusion of
the witnesses’ testimony. Appellant provides no support for his implied view that failure
to apply the least severe sanction is an abuse of discretion. Moreover, the supreme court
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has rejected appellant’s argument that exclusion is an unduly harsh sanction. See Lindberg
v. Health Partners, Inc ., 599 N.W.2d 572, 578 (Minn. 1999) (acknowledging that Minn.
Stat. § 145.682 “may have harsh results in some cases” but stating that the legislature chose
to enact a “policy of eliminating frivolous medical malpractice lawsuits by dismissal”).
The district court properly decided Mayo’s motion to exclude the untimely -
disclosed witnesses under the excusable -neglect standard established by Minn. Stat.
§ 145.682, subd. 4(c), and Mercer, 715 N.W.2d at 123. There was no abuse of discretion
in excluding the testimony of appellant’s untimely disclosed expert witnesses.
2. The Grant of Mayo’s Motion For JMOL
This court reviews a district court’s grant of JMOL de novo. Wall v. Fairview Hosp.
& Healthcare Servs., 584 N.W.2d 395, 406 (Minn. 1998).
Dr. J.G. wrote in his report:
One might be inclined to conclude that the serotonin syndrome
and the brain hemorrhage had been independent of one
another. . . . However, I can state with reasonable medical
certainty that the events played out in a very different way. To
be specific, it was the serotonin syndrome —induced directly
by the excessive doses of opioids and other pro -serotonergic
medications administered in the [Mayo] hospital —that set in
stage the chain of events directly leading to [ Koetz’s] demise.
Put differently, in the a bsence of the serotonin syndrome,
[Koetz] would be alive today.

Appellant’s attorney told the jury in her opening statement:

The evidence will show that serotonin syndrome is a serious
medical condition caused by an excess of serotonin, a
neurotransmitter in the brain. When someone experiences
serotonin syndrome, the levels of serotonin in their body
become[] dangerously high. . . . Serotonin syndrome can also
cause neurological symptoms such as seizures, loss of
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consciousness, and coma. These neurological effects can
further contribute to the life threatening nature of the condition.

. . . .

Tomorrow you will hear from our expert, a neurologist
by the name of [Dr. J.G. ]. . . . [He] will walk you through the
evidence . . . . Serotonin syndrome . . . killed [ Koetz] from a
massive, unchecked, unrecognized bleed in her head.

Based on Dr. J.G.’s report and appellant’s attorney’s opening statement, and in response to
Mayo’s request to limit the testimony of Dr. J.G., the district court said before witness
testimony, “I think we need to call [Dr. J.G.] in and [outside the presence of the jury] have
him elaborate in his report as to what he means by ‘the serotonin syndrome accounting for
her demise.’”
When the district court asked Dr. J.G. why he thought Koetz’s brain aneurism was
“connected to the serotonin syndrome,” Dr. J.G. answered,
I would say that there was just a very solid basis in the way that
the events were playing out. I would admit that we don’t really
have a perfect understanding of what took place, but I do think
that the signal events that were taking place [are] more
compatible with serotonin syndrome compared to anything
else, and the final event being the ruptured aneurysm just kind
of brought that further to the table.

When asked if Mayo’s alleged mistreatment or failed diagnosis was connected to or caused
the aneurism, Dr. J.G. answered that the aneurism was the final event. The district court
agreed, but again asked why Dr. J.G. thought the aneurism was “connected to the serotonin
syndrome.” Dr. J.G. answered,
I mean, the fundamental basis began with the serotonin
syndrome. I think this was the key moment that in many ways
from the moment that serotonin syndrome was building and
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wreaking havoc, it is my strong impression that, more likely
than not, that this kind of sequence, going from kind of small
bubbling amount of serotonin syndrome activity with the
additional compounding factors that were on board over the
couple days set up the nidus of kind of this perfect storm where
this is a syndrome and diagnosis that one always has to have
on their fingerprints [sic], because if you blink or if you delay
in the timing of that, I think, yes, there is a very sharp line in
terms of that projectory [sic].

When the district court asked Dr. J.G. a third time if it was his opinion “that the serotonin
syndrome created that massive head bleed?” Dr. J.G. answered, “Yes.” When the district
court asked, “[W]hat’s the basis for that opinion?” Dr. J.G. answered:
The basis for my opinion comes from my own personal
understanding of how this syndrome plays out, and I think the
key events were kicked off with the start of the serotonin
syndrome building, and then from there that brought additional
challenges--well, let me try and rephrase that.
So as I was saying, I do think that the serotonin
syndrome was the fundamental nidus of how all of this began
to snowball and cascade, and based on my understanding from
the literature and other sources, I think that [Koetz] was having
increasing difficulty maintaining her airway and so on. So I
think that as things progressed further, the serotonin syndrome
serving as that kind of principal nidus, ended up at a point
where [Koetz] was no longer able to kind of sustain--basically
sustain her basic vitals. So it is my impression that there was
kind of a--kind of like a jigsaw puzzle which increasingly came
to shape leading to the mechanism of aneurysmal rupture.

Dr. J.G. then asserted that nine articles cited in his report supported his view that, because
of serotonin syndrome, Koetz was “not able to sustain her basic vitals, . . . [which] leads to
. . . the bleeding in the brain.” Mayo’s counsel asked Dr. J.G. which article established “a
causal connection with aneurysmal rupture and serotonin syndrome.” Dr. J.G. responded
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by reading excerpts from two articles, neither of which discussed aneurysmal rupture or
cerebral hemorrhage.
When Dr. J.G. was asked if it was true that there was “no medical literature in the
world that provides a scientifically reliable dataset or reliable medical basis to draw a causal
connection between serotonin syndrome and aneurysmal rupture to intercrania l
hemorrhage,” he answered, “[W]hat you say, yes. In certain respects, it is true.”
After Dr. J.G. had testified, the district court stated:
I’m going to limit [Dr. J.G.’s ] testimony as to his other
statements within his report regarding the failure to follow the
standard of care and not ordering a CT scan and other things in
that line. I’m not going to allow him to testify further into the
idea as it relates to the massive head bleed caused by the
serotonin syndrome.
The court’s decision . . . is because . . . [t]he court tried
multiple different ways to get that testimony out of [Dr. J.G. ].
And until the court asked him directly, he wasn’t able, wasn’t
willing, didn’t provide the testimony, and I think that became
clear to the court as we went further along that he himself
expressed that he can’t say that with any certainty. So
foundationally I don’t think it is there. I don’t think he can say
that with any medical certainty, and so based upon that, the
court is limiting his testimony.

“For medical malpractice claims, we have generally held . . . that proving causation
required that a plaintiff must show that it is more likely than not that the defendant’s
conduct was a substantial factor in bringing about the result. That remains the c ausation
standard today.” Rygwall v. ACR Homes, Inc., 6 N.W.3d 416, 429 (Minn. 2024) (quotation
and citation omitted). Absent any evidence that Koetz’s aneurism and death were caused
by Mayo’s failure to correctly diagnose and treat her serotonin syndrome, the district court
did not err by granting Mayo’s motion for JMOL.
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Because th ere was no abuse of discretion in the district court’s exclusion of
appellant’s untimely disclosed expert witnesses and no error in the district court’s grant of
Mayo’s motion for JMOL, we affirm.
Affirmed.