Workers’ Compensation Law § 21 Presumption Applies to Unwitnessed Stair-Fall While Reporting Early to Change into Required Uniform; Rebuttal Requires Idiopathic Proof

Introduction

Matter of Mondesir v Allied Universal (2026 NY Slip Op 01829 [3d Dept Mar. 26, 2026]) concerns whether a catastrophic fall on workplace stairs—occurring shortly before the start of a shift while the claimant descended to a basement locker room to change into a required uniform—was a compensable workers’ compensation accident.

The claimant, Gregory Mondesir, worked as a security professional. He slipped on allegedly wet, slick stairs, fell head-first down a flight of stairs, and suffered a cervical spinal cord injury requiring emergency C4–C5 surgery, leaving him with profound functional limitations. The employer and carrier denied the claim, arguing (i) the fall was idiopathic (stemming from a personal medical condition rather than a workplace risk) and (ii) the fall occurred outside the scope of employment because it was pre-shift.

The Workers’ Compensation Board established the claim, applied the Workers’ Compensation Law § 21 presumption applicable to unwitnessed and/or unexplained workplace accidents, found the presumption unrebutted, and awarded temporary total disability benefits for the period at issue. The carrier appealed.

Summary of the Opinion

The Appellate Division, Third Department affirmed. It held that substantial evidence supported the Board’s findings that:

  • the fall was an unwitnessed and/or unexplained accident occurring in the course of employment, triggering the Workers’ Compensation Law § 21 presumption of compensability;
  • the carrier did not rebut the presumption because the record lacked medical opinions attributing the fall to idiopathic causes; and
  • medical evidence supported the finding that the claimant was temporarily totally disabled during the relevant period.

The court also endorsed the Board’s determination that descending to a basement locker room to change into a required uniform immediately before a shift was sufficiently work-related and did not constitute a deviation removing the claimant from the course of employment.

Analysis

Precedents Cited

The decision is built on a line of Third Department authority addressing (1) the fact-finding deference owed to the Board, (2) the Workers’ Compensation Law § 21 presumption for unwitnessed/unexplained accidents, (3) the evidentiary burden to rebut that presumption, (4) scope-of-employment principles for pre-shift or ancillary conduct, and (5) disability-degree review.

1) Deference to the Board and “substantial evidence” review

  • Matter of Duta-Zumba v Urban Atelier Group, LLC, 242 AD3d 1264 (3d Dept 2025): Cited for the principle that whether a compensable accident occurred is a question of fact for the Board and will not be disturbed when supported by substantial evidence. Mondesir uses Duta-Zumba both to frame appellate deference and later to emphasize the absence of medical evidence of idiopathic causation.
  • Matter of Bosque v Prime Support Inc., 226 AD3d 1280 (3d Dept 2024): Reinforces the two-part compensability requirement—injury must “arise out of” and occur “in the course of” employment—and supplies key language on the presumption and rebuttal.

2) Workers’ Compensation Law § 21 presumption for unwitnessed/unexplained accidents

  • Mattero of Docking v Lapp Insulators LLC, 179 AD3d 1275 (3d Dept 2020): Quoted (including its quotation of Babson) for the rule that Workers’ Compensation Law § 21 (1) provides a presumption of compensability for accidents during the course of employment that are unwitnessed or unexplained.
  • Matter of Babson v Finch Pruyn & Co. Inc., 25 AD3d 936 (3d Dept 2006): Serves as the foundational articulation (as quoted through Docking) of the presumption’s applicability to unwitnessed/unexplained events.
  • Matter of Silvestri v New York City Tr. Auth., 153 AD3d 1069 (3d Dept 2017); Matter of Wichtendahl v Arrow Bus Line, 307 AD2d 400 (3d Dept 2003); see also Matter of Fallon v National Gypsum Co., 53 AD2d 745 (3d Dept 1976), lv denied 40 NY2d 803 (1976): Cited as additional support that the presumption is a settled doctrine in the Third Department’s jurisprudence.

3) What it takes to rebut the presumption (idiopathic causation requires proof)

  • Matter of Bosque v Prime Support Inc., 226 AD3d at 1281-1282: Provides the burden-shifting framework: once the presumption applies, the carrier must present substantial evidence to the contrary that “precludes” the Board from crediting any explanation other than the employer’s. Mondesir applies this strictly—mere conjecture about a personal cause is insufficient.
  • Matter of Quigley v Concern for Ind. Living., 146 AD3d 1185 (3d Dept 2017); Matter of Worthington v Samaritan Med. Ctr., 124 AD3d 1155 (3d Dept 2015); Matter of Cartwright v Onondaga News Agency, 283 AD2d 837 (3d Dept 2001): Cited to support the conclusion that without competent evidence connecting the fall to an idiopathic cause, the presumption remains unrebutted.
  • Matter of Duta-Zumba v Urban Atelier Group, LLC, 242 AD3d at 1266 n: Used pointedly for the proposition that where “no medical opinions” link the fall to idiopathic reasons, rebuttal fails. Mondesir mirrors that evidentiary gap: neither the treating emergency physician nor the carrier’s consultant identified dehydration, syncope, intoxication, stroke, or another personal event as the cause.

4) Course of employment: pre-shift locker-room/uniform activity as work-related

  • Matter of Ramales v Frank & Nino's Pizza Corp., 238 AD3d 1454 (3d Dept 2025): Cited to support that claimant’s conduct did not deviate so far from employment as to be outside its scope. Mondesir applies Ramales to hold that going to a locker to change into a required uniform is sufficiently connected to the job.
  • Matter of Shyti v ABM, 192 AD3d 1309 (3d Dept 2021): Reinforces that certain preparatory or incidental acts tied to the job’s requirements can remain within the course of employment.

5) Disability degree: the Board’s discretion in weighing medical proof

  • Matter of Seide v Brooklyn Hosp. Ctr., 226 AD3d 1187 (3d Dept 2024): Cited for the rule that appellate courts will not disturb the Board’s disability-degree finding if supported by substantial evidence, even if a different outcome could have been reasonable.
  • Matter of Arias v U.S. Concrete, Inc., 198 AD3d 1052 (3d Dept 2021): Cited for the Board’s authority to evaluate medical opinions and accept or reject portions thereof.
  • Matter of Malerba v Ameron Global, Inc., 117 AD3d 1302 (3d Dept 2014); Matter of Ferguson v Fruehauf Corp., 156 AD2d 880 (3d Dept 1989): Cited as support that the medical record can adequately substantiate the Board’s disability assessment.

Legal Reasoning

1) The accident was within the course of employment despite being pre-shift

A central defense theme was temporal: the fall occurred “prior to the start” of the shift. The court, however, emphasized function over clock time. The claimant arrived a few minutes early to access a basement locker and change into a uniform he was required to wear and which was stored on-site. The court treated this as an act incidental to employment—an integrated part of reporting for duty—not a personal frolic.

In Footnote 2, the court expressly holds that descending the stairs toward the basement locker room to change into the required uniform was “sufficiently work-related,” and that claimant’s conduct did not deviate from the course of employment so as to remove him from coverage, invoking Matter of Ramales v Frank & Nino's Pizza Corp. and Matter of Shyti v ABM.

2) The presumption applied; the carrier could not rebut it without idiopathic evidence

Once the Board found the incident unwitnessed and/or unexplained and occurring in the course of employment, Workers’ Compensation Law § 21 shifted the evidentiary burden. The carrier attempted to suggest alternative personal causes (idiopathic fall), pointing to the claimant’s blood alcohol level (below legal intoxication) and potential alternative explanations such as dehydration or syncope.

The court’s reasoning is evidentiary and practical: rebuttal requires more than insinuation. Two medical witnesses were particularly damaging to the carrier’s position:

  • The attending emergency room physician testified the bloodwork was not “clinically significant,” did not attribute the fall to dehydration, and viewed the injuries as consistent with the stair fall observed on surveillance video.
  • The carrier’s own consultant (orthopedic surgeon) opined that the condition was causally related to slipping and falling down the stairs, found no evidence of stroke, myocardial infarction, or syncopal episode preceding the fall, and maintained that opinion even after reviewing the video.

With no medical opinion connecting the fall to an idiopathic cause, the court held—tracking Matter of Duta-Zumba v Urban Atelier Group, LLC and Matter of Bosque v Prime Support Inc.—that the presumption was not rebutted. The Board, as credibility arbiter, was entitled to accept the claimant’s account of wet, slick stairs and reject speculative alternatives.

3) Temporary total disability was supported by substantial evidence

On disability, the court applied the familiar standard from Matter of Seide v Brooklyn Hosp. Ctr. and Matter of Arias v U.S. Concrete, Inc.: the Board weighs the medical proof, and the appellate court intervenes only if substantial evidence is lacking.

The record contained consistent medical evidence of profound impairment—wheelchair use, inability to perform personal hygiene independently, quadriparesis, neuropathic pain syndrome, and traumatic brain injury—supporting a finding of 100% temporary total disability for the specified period. Even the carrier’s consultant supported total disability at the time of examination.

Impact

1) Strong reinforcement of § 21 in fall cases framed as “idiopathic”

Mondesir underscores that in unwitnessed/unexplained workplace falls, carriers must develop affirmative, competent proof of idiopathic causation to defeat compensability. Pointing to “possible” dehydration, low-level alcohol, or other speculative explanations—without a medical opinion tying those factors to the fall—will typically be insufficient.

2) Pre-shift preparatory conduct can still be “in the course of employment”

The decision also strengthens coverage for employees injured while engaging in preparatory acts closely tied to job requirements on the employer’s premises—here, accessing a locker and changing into a required uniform. Employers disputing course-of-employment on timing alone face an uphill battle where the activity is a functional prerequisite to performing the job.

3) Practical litigation consequences

  • For carriers: to rebut § 21 in an “idiopathic fall” theory, the record must include medical causation testimony (not merely abnormal labs or post-hoc conjecture) connecting a personal condition/event to the fall.
  • For claimants: consistent accounts of mechanism of injury, corroborative treating records, and even the carrier’s IME concessions can be decisive.
  • For employers: the “premises + required uniform/locker-room” context increases the likelihood that an injury will be found within the course of employment.

Complex Concepts Simplified

  • “Arising out of” vs. “in the course of” employment: “In the course of” concerns time/place/circumstances (were you at work or doing something connected to work?). “Arising out of” concerns causal connection (did a work-related risk contribute to the injury?).
  • Workers’ Compensation Law § 21 presumption: If an accident happens during the course of employment and is unwitnessed or unexplained, the law presumes it is compensable unless the employer/carrier proves otherwise with substantial evidence.
  • Idiopathic fall: A fall caused by a purely personal medical condition (e.g., fainting from a medical event) rather than workplace conditions. To use this defense effectively, the carrier generally needs medical proof linking the personal condition to the fall.
  • Substantial evidence: Not the “best” evidence, and not proof beyond a reasonable doubt—just enough relevant proof that a reasonable mind could accept to support the Board’s conclusion.
  • Temporary total disability: A finding that, for a period of time, the claimant is completely unable to work due to the work-related injury, even if future improvement is possible.
  • FROI/SROI forms: Administrative claims forms used in workers’ compensation (First/ Subsequent Report of Injury) reflecting notice, positions, and claim handling (including denials).

Conclusion

Matter of Mondesir v Allied Universal affirms two practical rules with significant reach in New York workers’ compensation litigation: (1) the Workers’ Compensation Law § 21 presumption remains a powerful mechanism in unwitnessed/unexplained workplace fall cases, and it cannot be rebutted by speculation untethered to medical causation evidence; and (2) pre-shift conduct that is functionally required by the job—such as accessing an on-site locker to change into a required uniform—can remain within the course of employment. The opinion further illustrates the deference appellate courts give to the Board’s credibility assessments and disability determinations when supported by substantial evidence.