Medical Causation in Increased-Harm Cases

A trial-strategy note for plaintiff’s counsel

Increased-harm causation is the legal theory that wins delayed-care cases. It is also the theory that loses them when the trial team treats it as a clinical argument rather than a story.

This page is about the second half — how to try an increased-harm causation case in front of a jury so that the abstract concept of “increased risk” lands as a concrete, intuitive, unavoidable conclusion. The framework here was tested and validated in O’Malley v. Diamond Resorts: a unanimous $60 million Orange County verdict on a record built entirely on this theory, then unanimously affirmed by the Fourth District Court of Appeal in November 2023 (G061459) against a direct appellate challenge to the sufficiency of the plaintiffs’ causation evidence. With CCP § 998 enhancements and statutory post-judgment interest, the final paid recovery exceeded $100 million.

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The legal standard, briefly

Under Restatement (Second) of Torts § 324A(a), adopted in California, a defendant who negligently performs an undertaking is liable when its conduct increased the risk of harm to the plaintiff. The plaintiff does not have to prove that the defendant caused the underlying medical event. The plaintiff has to prove that the defendant’s conduct made the outcome worse than it would have been with reasonable performance.

CACI No. 430 (Causation: Substantial Factor) requires that the defendant’s conduct be a “substantial factor” in causing the plaintiff’s harm. A substantial factor is more than a remote or trivial factor. It does not have to be the only factor.

That standard is, by design, lower than but-for causation. It is generous to plaintiffs. The challenge is not the law. The challenge is teaching the jury to use it.

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The jury’s instinct — and how to redirect it

When a jury hears that the plaintiff suffered a medical event (aneurysm, stroke, cardiac arrest, overdose), the instinctive thought is: that’s a medical problem. The doctors didn’t cause it. The hotel didn’t cause it. Why are we here?

The trial team’s job is to redirect that instinct without contradicting it. The aneurysm is not in dispute. Nobody is accusing the hotel of causing the aneurysm. What we are accusing the hotel of is a separate decision they made, in a separate place, at a separate time, that made the outcome of an unrelated medical event much worse.

The framing that works:

“Two things happened that night. The first thing was something nobody at the hotel caused — a brain aneurysm. The second thing was something the hotel had complete control over — whether to follow its own safety rules. We are here because of the second thing. The first thing was a medical event. The second thing was a choice.”

That framing introduces the right mental model in voir dire and never lets it go.

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Five trial-strategy moves that make increased-harm causation land

Move 1 — Use the hotel’s own policy as the starting point. The hotel wrote down what reasonable care looked like. The hotel’s policy is more persuasive than any plaintiff’s expert. The jury is being asked to find that the hotel did not meet its own standard, not some standard imposed by outsiders. Open with the policy on a board. Refer back to it in every closing.

Move 2 — Build the timeline as a comparison, not a narrative. Show two timelines side by side. The top one is what actually happened. The bottom one is what should have happened had the policy been followed. Each event in the top timeline has a paired event in the bottom timeline. The gap between them is the case.

ACTUAL                                | POLICY-COMPLIANT 9:14 PM  Husband calls front desk     | 9:14 PM  Husband calls front desk 9:21 PM  One worker arrives at door   | 9:21 PM  Two trained staff arrive 9:22 PM  Worker glances from doorway  | 9:22 PM  Staff enter and inspect fully 9:23 PM  Worker reports room empty    | 9:23 PM  Staff find plaintiff on floor | 9:24 PM  Staff call 911 9:24 PM  Husband begins driving       | 9:30 PM  Paramedics on scene 10:11 PM Husband finds plaintiff      | 9:50 PM  Plaintiff in ER 10:14 PM 911 called                    | 10:20 PM Neurosurgical intervention 10:42 PM Paramedics on scene           | 11:30 PM Plaintiff in ER               | 12:50 AM Neurosurgical intervention    |

The visual is more powerful than any direct examination. The jury sees the gap.

Move 3 — Anchor the causation expert in the timeline, not in probability percentages. The temptation is to have the neurosurgery expert testify in probabilities — “had treatment been initiated within 30 minutes, the plaintiff’s outcome would have been X% better.” Juries do not retain probability testimony. They retain time. Have the expert testify in time:

“Every minute of delay in treating a ruptured aneurysm has a measurable effect on the plaintiff’s outcome. A patient treated within 60 minutes typically achieves [specific functional outcome]. A patient treated after three hours typically achieves [specific worse outcome]. The plaintiff here received treatment more than three hours after the rupture began. The deficits she has are the deficits we see in patients who get treatment that late.”

Time becomes the unit. The jury can multiply time by harm.

Move 4 — Make the loss visible. Increased-harm cases are won by making the difference between what the plaintiff is and what they would have been visible. This means:

• Video of the plaintiff before the incident
• Family testimony about specific, concrete losses (not abstractions)
• Day-in-the-life video of the current reality
• Direct examination of the plaintiff if cognitively possible, even if brief

The jury’s compensation depends on what the jury sees. Show them what was lost.

Move 5 — Close on the choice, not the medicine. Closing argument should not be a medical seminar. It should be a moral argument about a choice the defendant made. The defendant chose to staff the front desk so thinly that the welfare-check policy could not be followed. The defendant chose to send an untrained worker. The defendant chose to ignore its own rules. Each of these is a choice. The jury is being asked to hold the defendant accountable for the choices, not for the medicine.

A quote that lands the moral argument:

“Safety rules must be followed. The welfare check policy must be done right because the consequence of that is life or death. You should not open your hotel for business if you’re not going to follow basic safety rules.” — Arash Homampour (Daily Journal, March 3, 2022)

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Cross-examination notes for the defense expert

The defense will retain an expert to opine that the outcome would have been the same with or without timely intervention. Cross should establish:

1. The expert is not the treating physician. They did not examine the plaintiff at the time of the event.
2. The expert is paid by the defense. Establish the rate, the hours, the prior work for the same defense firm and insurer.
3. The expert agrees that timing matters in the underlying condition. No qualified neurosurgeon will say timing is irrelevant. Get them to concede the principle and then narrow them on the application.
4. The expert’s opinion depends on assumptions about the plaintiff’s specific clinical picture. Challenge those assumptions with the contemporaneous medical records.
5. The expert is not opining that the hotel acted reasonably. They are confined to medical causation. The hotel’s conduct is not their domain. The jury should know that.

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The jury instruction package

Request the following instructions:

• CACI 400 (Negligence — Essential Factual Elements)
• CACI 401 (Basic Standard of Care)
• CACI 430 (Causation: Substantial Factor)
• CACI 431 (Causation: Multiple Causes)
• Special instruction on negligent undertaking drawn from § 324A and Artiglio

The substantial-factor instruction (430) is the workhorse. It does not require but-for causation. It says the defendant’s conduct must be “more than a remote or trivial factor.” That is exactly the standard the increased-risk theory needs.

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A note on the appellate posture

Diamond Resorts’ central appellate argument in O’Malley was that the plaintiffs failed to introduce competent evidence of causation at trial. The Fourth District rejected the argument and unanimously affirmed. The causation framework outlined on this page — treating physicians plus retained experts, expert testimony framed in time rather than probability, hospital records anchoring the timeline — survives appellate scrutiny in a case where the defense made causation its main appellate target.

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Refer or co-counsel

The Homampour Law Firm tries delayed-care and increased-harm causation cases throughout California. O’Malley v. Diamond Resorts: $60 million jury verdict, $100 million+ final paid judgment, unanimous appellate affirmance on a defense-driven causation challenge. We accept referrals and co-counsel arrangements on appropriate cases. Contact our office to discuss.

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Related pages

• The $60M O’Malley case study
• Negligent undertaking after O’Malley
• Defeating summary judgment in delayed-care cases
• Proving future medical for permanent memory loss

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Frequently Asked Questions

What is increased-harm causation?

Increased-harm causation is a California legal theory holding a defendant liable when its negligent conduct made the outcome of an underlying medical event worse than it would have been with reasonable care. The plaintiff doesn’t have to prove the defendant caused the medical event — only that the defendant’s conduct was a substantial factor in causing the increased harm.

What is the legal standard for substantial factor causation in California?

Under CACI No. 430, the defendant’s conduct must be a “substantial factor” in causing the plaintiff’s harm — more than a remote or trivial factor. It does not have to be the only factor. This standard is intentionally lower than but-for causation.

How should expert testimony be framed in an increased-harm case?

In time, not probability percentages. Juries do not retain probability testimony. They retain time. Have the medical expert testify: “A patient treated within 60 minutes typically achieves [outcome]. A patient treated after three hours typically achieves [worse outcome]. The plaintiff received treatment more than three hours after rupture.” Time becomes the unit the jury can multiply by harm.

What jury instructions should be requested?

CACI 400 (Negligence — Essential Factual Elements), CACI 401 (Basic Standard of Care), CACI 430 (Causation: Substantial Factor), CACI 431 (Causation: Multiple Causes), and a special instruction on negligent undertaking drawn from § 324A and Artiglio v. Corning Inc.

Did the O’Malley causation framework survive appeal?

Yes. Diamond Resorts’ central appellate argument in O’Malley v. Diamond Resorts was that the plaintiffs failed to introduce competent evidence of causation. The Fourth District Court of Appeal unanimously rejected the argument and affirmed the judgment in November 2023. The causation framework — treating physicians plus retained experts, testimony framed in time, hospital records anchoring the timeline — survives appellate scrutiny.