Mechanical engineering expert witness advises on retail slip and fall


Mechanical engineering expert witness advises on retail slip and fallA mechanical engineering expert witness advises on case involving a slippery store floor that caused a woman to fall and injure her knee and back. The plaintiff was shopping for deli products at a grocery store when she suddenly slipped on something wet and fell violently to the floor. She sustained serious injuries, including but not limited to her right knee and her entire back, which required medical attention.

She filed claims for negligence and premises liability against the store, alleging it knew or should have known that the premises were dangerous, defective and unsafe, and failed to take the reasonable measures necessary to cure the dangerous, defective and unsafe conditions or in the alternative to warn her of them.

Question(s) For Expert Witness

  • 1. What tests did you conduct?
  • 2. Was the floor dangerous when wet?
  • 3. What could the store have done to prevent the incident?

Expert Witness Response

I conducted slip resistance testing of the floor surface using a calibrated and validated English XL Tribometer under dry and wet conditions. It is my understanding that the floor surface at the time of my inspection was in a substantially similar condition to that which existed on the day of the incident.

The subject floor presented a substantial slip hazard for customers exercising reasonable care. According to the deposition testimony of the plaintiff, there was water present on the floor at the time of the incident. The testing I conducted at my site inspection revealed that the smooth vinyl composite tile floor surface had an average slip resistance of 0.87 under dry conditions and 0.22 when water was present. Studies of human ambulation have shown that a floor with a slip resistance of 0.22 presents a 45% chance of a slip event occurring, which is a substantially high risk. Therefore, it is my opinion the floor was in an unsafe condition at the time of the incident.

A water spill on the subject floor surface would be difficult to perceive. First, a puddle of water or other transparent liquids could easily go unnoticed by a customer because it would not provide an obvious visual contrast from the surrounding floor surface. Second, the extensive fluorescent lighting within the store reflects off the floor surface and mimics the appearance of a liquid. Third, within retail establishments, the attention of a customer is intentionally directed away from the floor and toward merchandise displays and advertisements. Therefore, it is my opinion that the combination of the above factors would make it difficult for a customer to perceive water or other transparent liquids on the subject vinyl floor surface.

Defendant failed to ensure the entire sales floor was in a reasonably safe condition for customers. Defendant knew of the high potential for spills to occur in many areas of the store and took measures to make these areas safer for customers. For example, large mats were placed at the entrance/exits, a hardwood floor was installed within the floral department, the produce department, and adjacent to the hot foods counter, and an abrasive vinyl tile was installed around the self-serve soup display. However, the reality is that spills can occur anywhere within a market at any time, particularly adjacent to refrigeration units, which are notorious for leaking. Given that the majority of the sales floor was a smooth vinyl tile, which is excessively slippery when wet, it is my opinion that defendant fell below the standard of care by failing to provide a reasonably safe floor for customers.

The smooth vinyl composite tile used for the majority of the sales floor was improper and inherently unsafe. Therefore, it is my opinion that no frequency of inspections or sweeps (even if conducted properly) could ensure that the floor was in a reasonably safe condition for customers. An abrasive slip-resistant vinyl tile floor throughout the entire sales floor would reduce the risk of a customer slip-and-fall incident occurring.

The expert is a mechanical engineer specializing in safety and pedestrian locomotion and vision (human factors). The expert has conducted investigations and analyzed more than 3,000 accident cases.

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