Background
Jacqueline Harris died from an acute pulmonary embolism approximately 30 days after undergoing a total knee replacement performed by orthopedic surgeon Dr. Jack Lennox. Harris’s estate sued Lennox, his employer Tri County Orthopedics, and Beaumont Hospital, alleging that Lennox’s failure to prescribe a prescription-strength anticoagulant constituted malpractice causing her death. The complaint was supported by an affidavit of merit (AOM) from Dr. B. Sonny Bal, who attested he was a licensed, practicing orthopedic surgeon during the year preceding the alleged May 2019 malpractice — a statutory prerequisite under MCL 600.2912d.
Plaintiff timely listed Dr. Bal as her sole orthopedic surgery expert. His deposition was scheduled for August 15, 2022, but he cancelled due to an emergency. After plaintiff’s counsel was unable to reschedule Bal, plaintiff filed an amended witness list substituting Dr. John Hall — without first seeking court permission. Defendants then uncovered deposition transcripts and LinkedIn records indicating that Bal had retired from clinical practice and teaching in November 2017, well before the May 2019 surgery, rendering his AOM facially invalid.
The Oakland Circuit Court struck the unauthorized amended witness list, denied plaintiff’s subsequent emergency motion to amend and a motion for voluntary dismissal, and ultimately granted summary disposition for Beaumont after concluding the AOM was invalid. The Court of Appeals reversed, holding the circuit court abused its discretion by failing to analyze all eight factors set forth in Dean v. Tucker, 182 Mich App 27 (1990), before effectively dismissing the case. Defendants sought leave to appeal to the Michigan Supreme Court, which ordered and heard oral argument.
The Court’s Holding
In a unanimous opinion authored by Justice Zahra, the Michigan Supreme Court held that the Dean factors are the wrong standard for evaluating a motion to amend a witness list. The governing standard is the “good cause” requirement of MCR 2.401(I)(2), which states that a court may bar an unlisted witness from testifying “except upon good cause shown.” The Dean factors were developed to guide courts imposing discovery sanctions — a context focused primarily on a party’s misconduct and noncompliance — and do not adequately center the inquiry on what matters most when a party seeks to substitute an expert: the moving party’s diligence and the prejudice flowing from granting or denying the motion. The Court therefore reversed the Court of Appeals on that legal point.
Nevertheless, the Court agreed with the Court of Appeals’ bottom-line conclusion that the circuit court abused its discretion — this time under the correct good-cause standard. The circuit court’s central finding was that plaintiff should have realized “much sooner than November 2022” that Bal was uncooperative or unqualified. The Supreme Court found this conclusion unsupported by the record: Bal had been cooperative and had offered dates as early as June 2022; much of the autumn 2022 delay was attributable to defendants’ own scheduling unavailability and their strategic pursuit of AOM-invalidity motions. The circuit court also mistakenly believed discovery closed June 7, 2022, when in fact a stipulated order extended it through December 12, 2022 — an error that infected its prejudice analysis.
Because the denial of the witness-list amendment was flawed, the subsequent grant of summary disposition — premised entirely on plaintiff’s inability to produce expert testimony — was also premature and could not stand. The Court remanded for further proceedings, and added that if the AOM were ultimately found defective, dismissal without prejudice (not with prejudice) would be the proper remedy absent a finding that plaintiff intentionally misused the AOM process to delay litigation.
Key Takeaways
- The standard for amending a witness list under MCR 2.401(I)(2) is “good cause” — not the eight-factor Dean v. Tucker test, which belongs to the discovery-sanctions context and is ill-suited for assessing a party’s diligence in securing expert witnesses.
- Good-cause analysis focuses on the moving party’s diligence (timeliness of the substitution motion, prior delays, status of discovery, prompt efforts to secure a replacement) and the prejudice to each side from granting or denying the amendment — not on misconduct or violations of prior court orders.
- A circuit court’s factual findings on diligence must be grounded in the actual record; misreading the discovery cutoff date or ignoring a party’s documented outreach efforts can independently constitute an abuse of discretion.
- Summary disposition entered solely because a plaintiff lacks a required expert witness is premature if the denial of leave to amend the witness list was itself an abuse of discretion.
- When a defective AOM is the basis for dismissal, the proper remedy is dismissal without prejudice unless the court finds the plaintiff intentionally exploited the AOM to gain extra filing time or delay proceedings.
Why It Matters
This decision resolves a recurring tension in Michigan trial courts between the Dean discovery-sanction framework and the plain language of MCR 2.401(I)(2). By firmly anchoring witness-list amendment motions to the good-cause standard, the Court gives litigants and trial judges clearer guidance: the dominant questions are diligence and prejudice, not the broader misconduct calculus imported from Dean. Defense counsel who have relied on Dean arguments to block expert substitutions will need to recalibrate their motion practice.
For medical malpractice practitioners in particular, the decision is a cautionary tale about the risks of relying on a single expert witness whose qualifications are later questioned. At the same time, it signals that courts must give plaintiffs a genuine opportunity — backed by an accurate understanding of the scheduling order — to substitute a compliant expert before the case is terminated on AOM grounds. The ruling reinforces Michigan’s general preference for resolving litigation on the merits rather than on procedural technicalities.