The loss of chance doctrine in civil tort law also known as the lost chance doctrine allows a plaintiff to recover damages when a defendant’s negligence eliminated or reduced a meaningful opportunity for a better outcome even when the plaintiff cannot prove that the negligence, by itself, more likely than not caused the ultimate harm.
In most personal injury cases, the plaintiff bears the burden of proving causation by a preponderance of the evidence. The loss of chance doctrine carves out a critical exception to that burden when the harm in question involved statistical probability rather than certainty.
Here is a thorough working knowledge of the loss of chance doctrine in U.S. civil tort law, covering its origin, how courts calculate damages under it, the states that have adopted it, real-world examples in medical malpractice and beyond, and the persistent legal debates surrounding its application.
If you are dealing with a loss of chance doctrine medical malpractice case, or if you are trying to understand how courts handle situations where the negligence did not definitively cause the harm but demonstrably reduced the plaintiff’s odds of avoiding it, this is the analysis you need.
The Core Problem the Loss of Chance Doctrine Solves
Traditional tort causation requires a plaintiff to prove that but for the defendant’s negligence, the harm would not have occurred. This works well in straightforward cases. A driver runs a red light and hits a pedestrian. But for the driver’s negligence, the pedestrian would not have been injured.
The problem arises in particularly medical malpractice cases where the plaintiff was already facing a risk of harm before the defendant acted. If a patient has cancer with a 40 percent chance of survival, and a physician negligently fails to diagnose it in time, that patient may die of the cancer months later.
Can the patient’s estate prove that the delayed diagnosis caused the death? Under traditional causation rules, probably not. The patient already had less than a 50 percent chance of survival even with proper treatment. The defendant’s negligence took a chance that was already less than even odds and reduced it further.
Applying the preponderance standard which requires the plaintiff to show greater than 50 percent probability that the negligence caused the death the plaintiff would lose in a traditional negligence action. The patient would have probably died anyway.
The loss of chance doctrine responds to this outcome by reframing what the injury actually is, so rather than treating the ultimate harm (death) as the compensable injury, the doctrine identifies the deprivation of a chance as the injury in itself.
That chance had real value, the defendant took it, therefore the defendant must pay for it.
Origin and Historical Development of the Loss of Chance Doctrine
The intellectual roots of the loss of chance doctrine in American tort law trace back to English contract law.
In the 1911 English case Chaplin v. Hicks, a plaintiff was prevented from attending an audition for a competition she had legitimately qualified for. The court allowed recovery for the loss of that opportunity even though no one could prove she would have won. The chance itself had measurable value, and its loss was compensable.
American courts began applying probabilistic reasoning to personal injury and medical malpractice contexts throughout the late 20th century. The landmark U.S. case most cited in this area is Herskovits v. Group Health Cooperative of Puget Sound, 664 P.2d 474 – Wash. 1983.
In Herskovits, a patient presented to a physician with symptoms that, if properly diagnosed, would have led to lung cancer treatment. The physician’s negligent failure to diagnose the cancer delayed treatment by approximately 14 months. By the time the cancer was properly diagnosed and treated, it had advanced significantly. The patient died.
Expert testimony established that with timely diagnosis, the patient had a 39 percent chance of survival. With the delayed diagnosis, his chance fell to 25 percent. He had already been below the 50 percent threshold before the negligence.
The Washington Supreme Court nevertheless allowed recovery, concluding that the reduced chance of survival was itself a compensable harm.
The Restatement (Third) of Torts has since grappled extensively with the doctrine. The Restatement takes the position that the loss of a chance can be a compensable injury in limited circumstances, particularly in medical malpractice contexts where the contractual nature of the physician-patient relationship creates a duty to maximize the patient’s chances of a good outcome.
How Courts Calculate Loss of Chance Damages
There are two primary approaches courts use when calculating damages under the loss of chance doctrine.
The Proportional Damages Approach
The most widely adopted approach in states that have accepted the doctrine calculates damages proportionally. The idea is straightforward: the plaintiff recovers not the full damages associated with the ultimate harm, but a fraction of those damages corresponding to the percentage chance that was lost.
The formula works like this:
take the total damages that would be awarded if the defendant were fully liable for the ultimate harm. Multiply that figure by the percentage of chance that the defendant’s negligence eliminated.
Suppose a patient had a 40 percent chance of surviving cancer with timely diagnosis. A physician’s negligence delayed the diagnosis, reducing the survival probability to 15 percent. The physician’s negligence therefore eliminated 25 percentage points of survival probability.
So if full wrongful death damages would be $1 million, the plaintiff recovers 25 percent of that figure which is $250,000 representing the proportional value of the chance that was destroyed.
This approach has the advantage of fitting neatly within the compensatory damages model that U.S. tort law prefers. The plaintiff receives exactly what the lost chance was wort; no more, no less.
The All-or-Nothing Approach to Loss of Chance
Some courts, and some scholars, reject the proportional approach entirely in favor of a threshold analysis.
Under this framework, courts ask only: is the evidence sufficient to support a finding that the defendant’s negligence more probably than not caused the ultimate harm? If the lost chance resulted in pushing the probability of harm past the 50 percent threshold, the plaintiff may recover full damages. If it did not, the plaintiff recovers nothing.
Critics of this approach argue that it produces arbitrary results and fails to compensate plaintiffs for real, documented harms. A physician whose negligence reduced a patient’s survival chance from 51 percent to 25 percent would face no liability under an all-or-nothing rule, even though that physician destroyed more than half the patient’s survival probability.
The proportional approach is increasingly favored, and the Restatement (Third) of Torts: Remedies has used the phrase “value of a chance” to describe the compensable interest; signaling academic and legal consensus that proportional recovery better reflects the actual harm.
States That Have Adopted the Loss of Chance Doctrine
The loss of chance doctrine has achieved majority adoption across the United States, though the specifics vary by jurisdiction. Research published in medical and legal journals, including analysis available through the National Institutes of Health’s PubMed Central, identified the following breakdown of state positions as of the most recent comprehensive review:
States that have adopted some form of the lost chance doctrine (31 jurisdictions):
Arizona, Connecticut, Delaware, District of Columbia, Hawaii, Illinois, Indiana, Iowa, Kansas, Louisiana, Massachusetts, Michigan, Minnesota, Mississippi, Missouri, Montana, Nevada, New Jersey, New Mexico, New York, North Dakota, Ohio, Oklahoma, Oregon, Pennsylvania, Puerto Rico, Washington, West Virginia, Wisconsin, Wyoming, and Utah.
States that have rejected the loss of chance doctrine (15 jurisdictions):
Alabama, Alaska, Florida, Idaho, Kentucky, Maryland, Maine, Nebraska, New Hampshire, North Carolina, South Carolina, South Dakota, Tennessee, Texas, and Vermont.
States that have deferred or not yet definitively addressed the issue:
Arkansas, Colorado, Rhode Island, and Virginia, among others.
Disclaimer: Individual factual scenarios can result in courts making exception-based rulings. If you are litigating a lost opportunity doctrine negligence claim, you must research current state-specific case law, as court positions evolve over time and some states have narrowed or expanded their adoption since earlier published reviews.
Real-World Examples of the Loss of Chance Doctrine in Civil Tort Cases
Example 1: Delayed Cancer Diagnosis in a Medical Malpractice Case
A patient presents to a primary care physician with a persistent cough, unexplained weight loss, and fatigue. The physician orders routine blood work but fails to order imaging studies that clinical guidelines would recommend given the symptom profile and the patient’s smoking history. A chest X-ray six months later, ordered by a different physician, reveals a lung mass.
By that point, the cancer has progressed from Stage II to Stage III. Expert testimony at trial establishes that at Stage II, the patient had a 45 percent five-year survival rate with appropriate treatment. At Stage III, the survival rate drops to 20 percent. The physician’s six-month delay in ordering imaging reduced the patient’s five-year survival probability by 25 percentage points.
Under the loss of chance doctrine as applied in states like Washington, Michigan, and Massachusetts, this 25-point reduction in survival probability constitutes a compensable injury. If full damages for a wrongful death are assessed at $2 million, proportional recovery would yield $500K to represent the value of the 25 percent survival chance that the physician’s negligence eliminated.
This type of case demonstrates why the lost chance doctrine is sometimes called the backbone of oncology-related medical malpractice litigation. Cancer staging is well-documented, survival statistics are tracked by the National Cancer Institute, and the causal link between diagnosis timing and outcome is often well-supported in medical literature.
Example 2: Failure to Administer a Time-Sensitive Emergency Treatment
Emergency medicine produces some of the clearest lost chance scenarios. A patient arrives at an emergency department with symptoms consistent with a stroke. Current clinical protocols recommend immediate administration of tissue plasminogen activator (tPA) for ischemic strokes within a defined time window. The physician fails to recognize the stroke presentation and discharges the patient.
The patient suffers permanent, severe neurological damage over the next several hours. Expert testimony establishes that had tPA been administered within the therapeutic window, the patient would have had a 40 percent chance of recovering functional independence with minimal neurological deficits. After the window closes without treatment, the opportunity to administer tPA was permanently lost.
The missed treatment window is the lost chance. The 40 percent probability of avoiding permanent neurological damage represents the value that the physician’s failure to diagnose destroyed. In jurisdictions that have adopted the doctrine, the patient can recover 40 percent of the damages representing the value of a life with functional independence.
This example is particularly significant because the harm is not eventual death but permanent disability.
Example 3: Failure to Refer to a Specialist in a Heart Attack Case
A patient presents to a general practitioner with chest discomfort, exertional shortness of breath, and an abnormal EKG. The practitioner attributes these symptoms to anxiety and stress and does not refer the patient to a cardiologist. Three months later, the patient suffers a myocardial infarction.
Due to the extent of the cardiac damage, which a cardiologist likely would have detected and treated prophylactically three months earlier, so the patient now has severely reduced cardiac function and cannot return to work
Cardiology experts at trial testify that with timely referral, there was a 55 percent likelihood that the patient’s coronary artery disease would have been identified and treated before the heart attack, and that with such treatment, the probability of the patient avoiding the severity of this cardiac event would have been 60 percent.
Under the loss of chance analysis, the question is not simply whether the practitioner’s failure caused the heart attack because that may be unprovable by a preponderance, but what chance of a better outcome the physician’s failure to refer cost the patient.
In states that recognize loss of chance damages, the plaintiff can recover a proportional award reflecting the specific probability that was eliminated.
Example 4: Missed Fracture on X-Ray Leading to Permanent Disability
Radiological misreading cases are a growing area of loss of chance doctrine litigation, so let’s say a patient presents to an urgent care facility with wrist pain following a fall and a radiologist misreads the X-ray as normal which caused the actual fracture (a scaphoid bone fracture) to go untreated for ten weeks. By the time a proper diagnosis is made, the fracture has developed avascular necrosis, a complication in which the bone tissue dies due to inadequate blood supply.
Expert testimony establishes that had the scaphoid fracture been properly identified and immobilized within the first 48 hours, the probability of avoiding avascular necrosis was 70 percent. The radiologist’s misreading eliminated that 70 percent chance.
The loss chance doctrine in this case applies not to death but to permanent functional impairment of the wrist. The plaintiff can recover proportionally: if full damages for permanent wrist disability are assessed at $500,000, recovery under the proportional lost chance approach yields $350,000, representing 70 percent of the total compensable harm.
This is just another example that illustrates the doctrine’s versatility. It is not exclusively a wrongful death doctrine. Any case in which a negligent act demonstrably reduced the probability of avoiding a documented harm may qualify for the loss of chance analysis.
Example 5: Failure to Treat Sepsis Aggressively in an ICU Setting
Hospital-acquired infections and sepsis management represent another category where lost chance of survival tort law claims frequently arise. A post-surgical patient develops early signs of sepsis including rising temperature, elevated white blood cell count, and falling blood pressure. Nursing staff document the signs but fail to alert the attending physician in accordance with the hospital’s protocol. By the time the physician is notified and orders aggressive treatment, the sepsis has progressed to septic shock.
The patient survives but suffers acute kidney injury requiring permanent dialysis. Expert testimony at trial establishes that had the sepsis protocol been followed within the recognized window of opportunity, the patient would have had a 65% probability of recovering without end-organ damage. The delay in treatment reduced that probability to approximately 15%, representing a 50% point reduction in the chance of avoiding permanent kidney failure.
Under the loss of chance doctrine, the patient can recover 50 percent of the damages attributable to the permanent kidney disease — a figure that, given the lifetime cost of dialysis, can represent an extremely substantial recovery even at half the total.
The Ongoing Legal Debate: Why Some States Reject the Doctrine
The states that have declined to adopt the lost chance doctrine do so primarily on two grounds.
- The first is the integrity of the preponderance of evidence standard. Courts in states like Texas, Florida, and Tennessee have expressed concern that allowing recovery for a lost probability lower than 50 percent fundamentally alters the burden of proof in negligence cases. These courts argue that once you permit recovery for a 30 percent lost chance, you are allowing plaintiffs to win negligence cases on a less-than-preponderance showing, which undermines the predictability and fairness of the tort system.
- The second concern involves double recovery and consistency. If a patient had a 40% pre-negligence chance of survival and the negligence reduced it to zero, a court applying a strict traditional analysis might still allow recovery if the patient’s estate can show by other evidence that the negligence was the primary driver of the ultimate outcome. Allowing an additional recovery under loss of chance theory in those circumstances risks compensating the same harm twice.
Supporters of the doctrine respond that these concerns misread what the doctrine actually does. The compensable injury is the probability itself; not the death or disability.
The proportional damages model ensures that defendants pay only for what they actually took. And for plaintiffs who already faced a less-than-even chance, the traditional preponderance standard would deny them any remedy at all, even when a physician clearly and demonstrably worsened their situation.
What a Loss of Chance Claim Requires You to Prove
If you or someone you represent is pursuing a loss of chance doctrine claim, the core elements you must establish include:
- The existence of a duty owed by the defendant to the plaintiff. In medical malpractice, this is established by the physician-patient relationship. In other contexts, duty must be analyzed under general negligence principles.
- A breach of that duty through conduct that fell below the applicable standard of care. Medical expert testimony is almost always required to establish standard of care in malpractice cases.
- The existence of a quantifiable probability that, at the time of the breach, the plaintiff had some meaningful chance of a better outcome. This is frequently expressed as a percentage and must be grounded in peer-reviewed medical literature, clinical guidelines, or documented statistical data.
- The defendant’s breach reduced or eliminated that probability. This causal link requires expert testimony establishing the connection between the specific negligent act and the reduction in the plaintiff’s probability of a better outcome.
- Damages. The damages calculation, as explained above, is typically proportional to the percentage of chance that was lost.
Why This Doctrine Matters Beyond Medical Malpractice
While loss of chance doctrine civil torts claims are most commonly litigated in medical malpractice contexts, the doctrine’s principles have been applied and debated in other civil tort settings as well.
Landlord-tenant litigation involving toxic exposures, where causal proof is inherently statistical, represents an emerging area of application. Environmental tort cases involving cancer clusters and probabilistic causation are another frontier where lost chance reasoning has been invoked.
The doctrine is ultimately about fairness in cases where a defendant’s negligence operated on a statistical playing field. Where a defendant demonstrably reduced a plaintiff’s odds of avoiding harm, tort law increasingly demands an accounting for that reduction and not merely for the ultimate outcome.
In Summary
The loss of chance doctrine reframes the compensable injury in cases where traditional causation proof is impossible because the plaintiff already faced a risk of harm.
It allows recovery proportional to the probability that was eliminated by the defendant’s negligence.
It is most developed in medical malpractice law but applies wherever a negligent act demonstrably reduced a plaintiff’s statistical chance of a better outcome.
