Can Expert Testimony Prove What Caused a California Slip-and-Fall? Osaze v. Gee

Almost every contested slip-and-fall case in Los Angeles County eventually comes down to one sentence in a defense motion: “Plaintiff cannot identify what caused the fall.” It is the single most effective weapon insurers and property owners have, and it has ended thousands of otherwise legitimate claims at the summary judgment stage — before a jury ever heard about the greasy floor, the unmarked step, or the broken handrail.

The published First District opinion in Osaze v. Gee, filed September 29, 2026, pushes back. The Court of Appeal reversed summary judgment for the property owner, concluding that the plaintiff’s expert declarations — addressing the physical condition of the walking surface and the biomechanics of the fall — supplied a reasonable, non-speculative basis for a jury to find causation. The practical message: a plaintiff who cannot narrate the moment of the fall in cinematic detail is not automatically out of court.

This guide explains what the decision means, how California slip-and-fall causation actually works, and what you should do right now if you were hurt on someone else’s property in Los Angeles.

The “You Can’t Prove Why You Fell” Defense

To win a California premises liability case, an injured person must prove four things: (1) the defendant owned, leased, occupied, or controlled the property; (2) the defendant was negligent in the use or maintenance of the property; (3) the plaintiff was harmed; and (4) the defendant’s negligence was a substantial factor in causing that harm. That fourth element — causation — is where cases die.

Defense counsel exploit a genuine feature of falls: they happen in a fraction of a second, often to people who are mid-stride, carrying something, or simply not looking at the ground, and who are then concussed or in shock. At deposition the plaintiff is asked, “Did you see the substance before you fell?” No. “Can you tell me, as you sit here today, exactly what your right foot contacted?” No. That transcript then becomes the centerpiece of a motion arguing that any verdict for the plaintiff would rest on conjecture.

California courts have long said that where the plaintiff’s theory requires the jury to choose between equally plausible causes, the claim fails as a matter of law. But courts have equally long held that causation may be proven by circumstantial evidence and reasonable inference — the plaintiff does not need an eyewitness or a confession. Osaze sits squarely in that second line of authority.

What Osaze v. Gee Actually Decided

The procedural posture matters more than the facts. The trial court granted summary judgment to the property owner, treating the plaintiff’s expert declarations as insufficient to raise a triable issue on causation. The First District reversed in a published opinion, and the reasoning breaks down into three points that Los Angeles practitioners will use immediately:

1. Expert declarations can bridge the gap between condition and fall

Where a qualified expert explains, with a reasoned basis, how a specific defective condition would produce the type of fall and the pattern of injury the plaintiff suffered, that opinion is evidence — not speculation. The expert supplies what the plaintiff’s own memory cannot.

2. “Speculation” is about the absence of reasoning, not the absence of certainty

An expert opinion is properly disregarded when it rests on assumptions with no evidentiary support or offers a conclusion with no explanation. An opinion grounded in measurements, slip-resistance standards, site inspection, photographs, and accepted methodology is not speculation merely because the expert was not present when the plaintiff fell.

3. On summary judgment, doubts go to the plaintiff

The court reaffirmed the familiar but frequently under-enforced rule: the moving party’s evidence is strictly construed, the opposing party’s evidence is liberally construed, and any doubt about whether an expert declaration creates a triable issue is resolved in favor of the party opposing the motion. Credibility contests between competing experts belong to a jury.

Which Experts Matter in a Los Angeles Slip-and-Fall Case

Expert type	What they establish
Safety / premises engineer	Coefficient of friction testing, ANSI and ASTM slip-resistance standards, whether the surface met industry norms when wet
Human factors specialist	Whether a reasonable person would have perceived the hazard — critical for open-and-obvious and comparative fault defenses
Biomechanical expert	Links the mechanism of the fall to the injury pattern (a slip produces a different injury signature than a trip)
Code / building consultant	Los Angeles Building Code and Title 24 violations: riser height inconsistencies, missing handrails, inadequate lighting, non-compliant ramps
Retail operations expert	Whether sweep schedules and inspection intervals met reasonable commercial practice — central to the notice element
Treating physicians and life care planners	Causation of the medical condition and the cost of future care

Causation is not the only fight — notice still matters

Even with strong expert causation evidence, a plaintiff must usually show the owner created the hazard, knew about it, or should have discovered it through reasonable inspection. In practice this is won with sweep logs, employee testimony about inspection intervals, surveillance footage showing how long a spill sat, and prior incident reports for the same location. Those records are time-sensitive — many Los Angeles retailers overwrite video within 14 to 30 days.

Where These Cases Happen in Los Angeles

Los Angeles produces a distinctive mix of premises claims because of how the city is built and how people move through it:

• Grocery and big-box stores — produce misters, freezer condensation, and tracked-in rain during the winter storm season. Downtown, Koreatown, and the mid-Wilshire corridor generate a steady volume.
• Multi-level parking structures — sealed concrete with worn traction coatings, oil sheen, and unmarked grade changes from Century City to LAX.
• Apartment common areas — exterior stairs and walkways in older Mid-City, Hollywood, and Valley buildings, where handrail and lighting violations are common.
• Restaurants and bars — kitchen pass-throughs, patio tile that polishes smooth, and poorly lit steps between dining levels.
• Public sidewalks and transit facilities — uplifted sidewalk panels from ficus roots, Metro stations, and city-owned plazas.
• Hotels and short-term rentals — pool decks, polished lobby stone, and bathtubs without slip treatment.

How Comparative Fault Works After a Fall

Expect the defense to argue you were distracted, wearing inappropriate footwear, intoxicated, or ignoring a warning cone. California applies pure comparative fault: your damages are reduced by your percentage of responsibility, but you are never barred from recovering. A jury that awards $400,000 and assigns you 30 percent of the blame still produces a $280,000 judgment. Defense adjusters routinely overstate comparative fault in early negotiations precisely because claimants do not know this.

The “open and obvious” defense is similarly oversold. A condition being visible does not automatically defeat liability; California law recognizes that an owner may still be liable where it is foreseeable that a person would encounter the hazard anyway — for example, the only path to the restroom, or a parking structure stairwell with no alternative route.

What to Do in the First 30 Days

1. Report the fall in writing and obtain the incident report number. Verbal reports vanish.
2. Photograph everything — the hazard from multiple angles and distances, the lighting, any warning signs present or absent, and the shoes you were wearing. Keep those shoes unwashed in a bag; experts test them.
3. Get medical care immediately. Gaps in treatment are the second-most common reason claims lose value.
4. Identify witnesses and capture phone numbers before anyone leaves.
5. Have counsel send a litigation hold letter for surveillance video, sweep logs, maintenance records, and prior incident reports at that location.
6. Do not give a recorded statement to the property owner’s insurer before you have advice. Those transcripts become summary judgment exhibits.
7. Stay off social media about the incident and your activities.
8. Calendar the deadlines — six months for public entities, two years otherwise.

If your injury came from a vehicle collision rather than a property hazard, see our guide for a Los Angeles car accident lawyer. For a full overview of premises claims, visit our Los Angeles slip and fall lawyer page, or contact our team directly.

Frequently Asked Questions

Sources & Citations

• Osaze v. Gee (Cal. Ct. App., 1st Dist., filed Sept. 29, 2026) — published opinion reversing summary judgment on causation, California Courts opinions.
• Cal. Code Civ. Proc. § 437c — summary judgment standard.
• Cal. Code Civ. Proc. § 335.1 — two-year statute of limitations for personal injury.
• Cal. Gov. Code §§ 911.2, 945.4 — government claim presentation requirements.
• Cal. Gov. Code § 830.2 — trivial defect / not dangerous condition as a matter of law.
• CACI Nos. 1000–1011 (premises liability), 430 (substantial factor causation), 405 (comparative fault).
• Cal. Evid. Code §§ 801–802 — basis and limits of expert opinion testimony.