Dierl v. Birkin, 525 P.3d 127

In Feb 2015 Dierl had a head CT after a ski injury; radiologist Birkin read it as negative and did not report a tumor.
By Nov 2015 Dierl developed neurologic symptoms; a later CT showed a brain tumor; he underwent a right pterional craniotomy in Dec 2015 and suffered permanent vision loss and pituitary damage.
Dierl sued Birkin for medical malpractice, alleging the missed Feb 2015 diagnosis allowed tumor growth that worsened surgical outcomes.
Neurosurgeon 1 (plaintiff’s disclosed expert) testified in deposition that the tumor enlarged ~4 mm over nine months and that earlier surgery likely carried lower risk, but he repeatedly stated he could not say to a reasonable degree of medical probability that earlier surgery would have prevented Dierl’s exact injuries.
Neurosurgeon 1 later submitted an affidavit asserting the delay caused greater vision loss; Neurosurgeon 2 (disclosed belatedly as rebuttal) submitted an affidavit attributing significant growth and a worse visual outcome to the delayed diagnosis.
The district court excluded Neurosurgeon 1’s affidavit as contradictory to his deposition (Webster v. Sill) and excluded Neurosurgeon 2’s affidavit from the plaintiff’s case-in‑chief as untimely under Rule 26; it granted summary judgment to Birkin for lack of admissible expert causation evidence.

Issue	Plaintiff's Argument	Defendant's Argument	Held
Whether Neurosurgeon 1’s affidavit may create a triable issue despite contradicting his deposition	Dierl: affidavit shows delay caused greater vision loss and thus proximate cause	Birkin: deposition testimony showed Neurosurgeon 1 could not state causation to medical probability; affidavit contradicts deposition and is barred	Court: Excluded the affidavit under Webster v. Sill because it contradicted clear deposition answers and offered no adequate explanation
Whether Neurosurgeon 2’s late‑produced affidavit may be used in plaintiff’s case‑in‑chief	Dierl: Rule 26 is inapplicable or Neurosurgeon 2 may be used as rebuttal; alternatively Rule 56 should permit admission	Birkin: late disclosure violated Rule 26; using rebuttal expert to supply an essential element of plaintiff’s case is improper and prejudicial	Court: Excluded Neurosurgeon 2 for failure to timely disclose under Rule 26; plaintiff bore burden to show harmlessness or good cause and did not do so
Whether the district court erred by not admitting Neurosurgeon 2 under Rule 56	Dierl: court should have allowed him an opportunity to cure under Rule 56(e)	Birkin: court reasonably exercised discretion in choosing summary judgment after exclusion under Rule 26	Court: No error; Rule 56 affords various remedies and granting summary judgment was within the court’s discretion

Webster v. Sill, 675 P.2d 1170 (Utah 1983) (deposition testimony that is clear and unmodified bars later contradictory affidavit absent adequate explanation)
Ruiz v. Killebrew, 459 P.3d 1005 (Utah 2020) (expert testimony generally required to establish proximate cause in medical malpractice)
Blank v. Garff Enters. Inc., 482 P.3d 258 (Utah Ct. App. 2021) (timely expert disclosures are essential; late expert disclosures are typically excluded absent harmlessness or good cause)
Keystone Ins. Agency, LLC v. Inside Ins., LLC, 445 P.3d 434 (Utah 2019) (burden to show harmlessness or good cause rests with the party seeking relief from Rule 26)
Salo v. Tyler, 417 P.3d 581 (Utah 2018) (summary judgment standard where defendant shows plaintiff lacks evidentiary basis for claim)
Jensen v. IHC Hosps. Inc., 82 P.3d 1076 (Utah 2003) (elements of a prima facie medical malpractice claim)