Background
Jacqueline Harris underwent a total knee replacement performed by orthopedic surgeon Jack D. Lennox, D.O., in May 2019. Dr. Lennox advised Harris to take aspirin post-surgery. Approximately 30 days later, Harris died from an acute pulmonary embolism. Her estate, through personal representative Lawanna Smith, filed a medical malpractice complaint in Oakland County Circuit Court against Dr. Lennox, his employer Tri County Orthopedics, PC, and Beaumont Hospital, alleging that Lennox’s failure to prescribe a prescription-strength anticoagulant caused her death. The complaint was accompanied by an affidavit of merit (AOM) signed by orthopedic surgeon B. Sonny Bal, M.D., who attested that he had been a licensed, practicing orthopedic surgeon during the year preceding the alleged malpractice.
Plaintiff timely named Dr. Bal as her sole orthopedic surgery expert. The parties scheduled his deposition for August 15, 2022, but Bal cancelled due to an emergency. After plaintiff’s counsel was unable to obtain new deposition dates from Bal, plaintiff filed an amended witness list substituting Dr. John Hall, M.D., without first seeking court permission. Defendants moved to strike the substitution. During the ensuing litigation, defendants discovered that Bal had retired from the practice and teaching of medicine in November 2017 — nearly two years before the May 2019 surgery — rendering his AOM potentially invalid under MCL 600.2912d. The circuit court struck plaintiff’s amended witness list, denied her subsequent motion to amend and her motion for voluntary dismissal, and ultimately granted summary disposition on the ground that the AOM was invalid, closing the case against plaintiff.
The Court of Appeals reversed, holding that the circuit court was required to consider all eight factors from Dean v. Tucker, 182 Mich App 27 (1990), before effectively dismissing a case by barring an expert witness, and that the court’s failure to do so was an abuse of discretion. Defendants sought leave to appeal in the Michigan Supreme Court, which ordered oral argument on the applications.
The Court’s Holding
In a unanimous opinion authored by Justice Zahra, the Michigan Supreme Court held that the correct standard governing a motion to amend a witness list is the good-cause standard set forth in MCR 2.401(I)(2), not the multi-factor test from Dean v. Tucker. The Court reasoned that MCR 2.401(I)(2) is stated in plain terms — a court may prohibit an unlisted witness from testifying “except upon good cause shown” — and there is no basis to depart from that plain language. The Dean factors were developed to guide imposition of discovery sanctions that result in dismissal; they focus primarily on party misconduct and violations of discovery orders, not on whether a party exercised diligence in securing an expert witness, which is the central inquiry under a good-cause analysis. The relevant considerations under the good-cause standard include the timeliness of the motion after discovering a witness’s unavailability, the absence of prior delays, the status of the discovery period, and the prejudice — defined as unnecessary expense caused by a lack of due diligence — that either party would incur.
Although the Court of Appeals applied the wrong legal standard, the Supreme Court agreed with its ultimate conclusion that the circuit court abused its discretion. Applying the correct good-cause framework, the Court found the record showed plaintiff had acted diligently: Dr. Bal was cooperative and had offered deposition dates as early as June 2022; defendants, not plaintiff, were unavailable for much of the scheduling period; and much of the September–October 2022 delay arose from defendants’ challenge to Bal’s AOM qualifications. The Court also noted the circuit court operated under a material factual error — it believed discovery had closed on June 7, 2022, when in fact the parties had stipulated to extend it through December 12, 2022. Because the denial of plaintiff’s motion to amend was flawed, the summary disposition predicated on that denial was premature and likewise required reversal. The Court additionally observed that, absent a finding of intentional misconduct by the plaintiff, any dismissal for a defective AOM must be without prejudice under Kirkaldy v. Rim, 478 Mich 581 (2007).
The Court reversed in part the Court of Appeals’ judgment and remanded to the circuit court for further proceedings consistent with the opinion.
Key Takeaways
- Michigan trial courts must apply the MCR 2.401(I)(2) good-cause standard — not the Dean v. Tucker eight-factor test — when ruling on a motion to amend a witness list to add or substitute an expert witness.
- The good-cause inquiry centers on the moving party’s diligence in discovering and responding to a witness’s unavailability, and on prejudice defined as unnecessary expense attributable to a lack of due diligence — not on the broader misconduct-focused factors relevant to discovery sanctions.
- A circuit court abuses its discretion when it denies amendment based on a misreading of the discovery schedule or by attributing to a plaintiff delays that were caused by the opposing party or by the witness’s own sudden unavailability.
- When a defective affidavit of merit is the basis for dismissal, dismissal must be without prejudice — preserving any remaining limitations period — unless the court finds the plaintiff intentionally used the defective AOM to improperly delay proceedings.
Why It Matters
This decision resolves a recurring uncertainty in Michigan civil litigation about which standard governs witness-list amendment motions. By grounding the analysis firmly in MCR 2.401(I)(2) and rejecting the wholesale importation of the Dean sanction factors into a different procedural context, the Court gives trial courts a clearer, more focused framework and guards against the risk that procedurally strict rulings on witness substitution will effectively terminate meritorious cases without an adjudication on the merits.
For medical malpractice practitioners in particular, the decision is significant because expert witnesses are indispensable at every stage — from the AOM at filing through trial — and witness availability problems are not uncommon. The ruling signals that a plaintiff who responds promptly and diligently when an expert becomes unavailable, and who can offer a replacement within the open discovery period, has a strong claim to good cause for amendment. Courts cannot short-circuit that inquiry by defaulting to sanction-oriented factors designed for a different purpose.