Unwitnessed Falls and Causation in California, Explained

By Alex (J.D. candidate, not a lawyer)

California appellate courts have held that a fall with no eyewitness does not, by itself, rule out proof of causation. Two published opinions say so: Kaney v. Custance (2022) and Osaze v. Aparicio-Gee (2026). Both cases are about summary judgment, a pretrial stage, and neither decided who was at fault.

This page explains what each court said, in the courts' own words where possible. It is general information about the law.

The short version

  1. Causation asks whether a defendant's conduct was a substantial factor in the harm.
  2. A missing eyewitness does not by itself end the causation question.
  3. Circumstantial evidence can support a reasonable inference about how a fall happened.
  4. Expert opinions on a fall's cause still face a court's gatekeeping review.
  5. At summary judgment, a court asks whether facts are disputed.
  6. Both cases reversed summary judgment; neither decided liability.

Causation in general terms

What the law says. The Osaze court began with this rule: "Causation is established for purposes of California tort law if the defendant's conduct is a 'substantial factor' in bringing about the plaintiff's injury." (Osaze, quoting Liberty Surplus Ins. Corp. v. Ledesma & Meyer Construction Co. (2018) 5 Cal.5th 216)

The court noted that causation is ordinarily a question of fact.

Read the official text

What it means in general. In a negligence or premises case, causation is the link between what a defendant did or failed to do and the harm that followed. The test the court described is whether the conduct was a "substantial factor." A question of fact is one that a jury usually decides after hearing the evidence. That is why the two cases below focus on whether the evidence was enough to reach a jury.

Kaney v. Custance (2022): a fall the plaintiff did not remember

What happened. The plaintiff fell on a two-step bathroom stairway that had no handrail. She remembered being on the stairs and waking up on the floor, and she did not remember the fall itself. The trial court granted summary judgment, and the Court of Appeal reversed.

What the court said. The opinion opens with a question and an answer: "Is a plaintiff barred as a matter of law from proving causation in a slip and fall case if there were no witnesses to the fall and he or she remembers being on stairs and then waking up in pain but does not remember the fall itself? No. That is not the law in California." (Kaney v. Custance (2022) 74 Cal.App.5th 201, 204)

The court then stated this rule: "A slip-and-fall plaintiff need not remember her fall to recover damages provided the evidence gives rise to a reasonable and probable inference that the defendant's negligence was a substantial contributing factor." (Kaney v. Custance (2022) 74 Cal.App.5th 201, 217)

Read the official text

What it means in general. The rule is about what evidence can go to a jury. In Kaney, the court held that the circumstances, including the condition of the stairs and the plaintiff's memory of being on them, could let a jury draw a reasonable inference about the cause of the fall. The court also treated causation in that case as within common knowledge, so expert testimony was not needed for that element.

Osaze v. Aparicio-Gee (2026): a fall no one saw

What happened. A woman followed a dog that escaped a grooming room at a veterinary hospital and fell in the hallway. No one saw the fall, and the door to the grooming room was propped open. One of the family's expert engineers measured a rise of about 1.25 inches at the doorway threshold.

She later died, and her husband and son brought a wrongful death suit against the hospital's owner and the building owner. The trial court excluded key parts of the family's expert opinions and granted summary judgment. The Court of Appeal reversed.

Read the official text

The court's gatekeeping role (Sargon)

What the law says. Evidence Code sections 801 and 802 govern expert opinion testimony. Section 801 covers what an expert opinion may be about and what it may be based on. Section 802 lets a witness explain the reasons for an opinion and what it rests on.

Read the official text of section 801 and section 802

In Sargon, the California Supreme Court held that under Evidence Code sections 801, subdivision (b), and 802, "the trial court acts as a gatekeeper to exclude expert opinion testimony that is (1) based on matter of a type on which an expert may not reasonably rely, (2) based on reasons unsupported by the material on which the expert relies, or (3) speculative." (Sargon Enterprises, Inc. v. University of Southern California (2012) 55 Cal.4th 747, 771-772)

The same opinion describes the limits of that role: "The court must not weigh an opinion's probative value or substitute its own opinion for the expert's opinion." The court instead "must simply determine whether the matter relied on can provide a reasonable basis for the opinion or whether that opinion is based on a leap of logic or conjecture." (Id. at p. 772)

Read the opinion (Caselaw Access Project scan of the official reports)

What it means in general. Before a jury hears an expert, the trial judge screens the opinion. The judge looks at what the expert relied on and how the expert reasoned. The judge can keep out opinions that are speculative or that rest on reasons the material does not support. The judge does not decide which expert is more convincing.

What Osaze held. The Court of Appeal said the trial court labeled the experts' opinions as speculation without doing that analysis. In the court's words, "simply labelling an opinion as 'speculation' does not make it so." The court also said: "The trial court's supposition that expert evidence about the cause of an 'unwitnessed' accident is necessarily 'speculative' and inadmissible is wrong as a matter of law."

The court explained that the experts looked at the conditions at the scene, took measurements, ruled out other possible reasons for the fall, and reached reasoned conclusions based on biomechanical principles. It held that the opinions should not have been excluded.

Summary judgment and the court's issue-finding role

What the court said. Quoting its own 2025 opinion in Birdsall v. Helfet, which in turn quoted a civil procedure practice guide, the court said: "The court's sole function on a motion for summary judgment is issue-finding, not issue-determination."

The court then turned to the missing eyewitness: "The absence of a witness to the fall no more provides a basis for granting summary judgment than it does for excluding the expert testimony."

Read the official text

What it means in general. Summary judgment lets a court end a case before trial when there is no real dispute about the important facts. At that stage, the judge looks for disputed facts and leaves it to a jury to resolve them. The judge must read the evidence in favor of the side opposing the motion. In Osaze, the court held that a jury could reasonably infer how the fall happened from the expert opinions and the other evidence, so the case should go forward.

What the court ordered

What the court said. "The judgment is reversed and the matter is remanded with instructions to the trial court to vacate its order granting the motion for summary judgment and to enter a new order denying the motion."

What it means in general. The case goes back to the trial court, which must deny the motion for summary judgment. The case then continues in the trial court.

What these cases do not decide

Neither opinion holds that any property owner was negligent or liable. Both concern what evidence can reach a jury. A jury, or a later ruling, decides the rest. Each case turned on its own record, including the specific conditions, testimony, and expert opinions in that case.

Status of the 2026 opinion

Osaze v. Aparicio-Gee was filed September 29, 2026. A party may still ask the California Supreme Court to review it. Under the California Rules of Court, a decision like this one generally becomes final in the Court of Appeal 30 days after it is filed, and a petition for review is due within 10 days after that (rules 8.264(b)(1), 8.500(e)(1)).

Sources

SentryHall publishes general legal information for educational purposes. It is not legal advice, and reading it does not create an attorney-client relationship. The author is a law student, not a lawyer. Laws change and apply differently to different facts. For advice about your situation, talk with a lawyer licensed in California. You can look up a lawyer's license status at calbar.ca.gov.

Official California resources: Self-Help Guide to the California Courts, State Bar attorney license search, and the State Bar list of certified lawyer referral services.

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