In a standard medical malpractice claim, the plaintiff must prove, by a preponderance of the evidence (or 51%, more likely than not) that the defendant doctor’s wrongful conduct caused the resulting injury. So for example, the dangerous medication dosage the doctor prescribed more likely than not (51%) caused the patient to have a heart attack resulting in physical disabilities.

But what about a situation where a patient is suffering from, for example, a pre-existing condition, like cancer? What if the treating doctor fails to recognize the obvious signs of debilitating disease and there is a delay in diagnosis resulting in the loss or reduction of the chances of a more favorable outcome, or even cure? The delay obviously did not cause the disease. And the patient, even with a timely diagnosis, was perhaps going to die. What if the doctor’s negligence resulted in a 20% reduction in the patient’s chance of survival? Under a loss of chance theory, the patient could pursue a claim for loss of a chance of a better outcome.

One can envision a myriad of facts that would fall under this theory. However, lost chance claims can be divided into two categories: lost chance of survival and lost chance of a better outcomeHerskovits v. Grp. Health Coop. of Puget Sound,99 Wn.2d 609, 664 P.2d 474 (1983)Mohr v. Grantham, 172 Wn.2d 844, 262 P.3d 490 (2011).

Lost Chance of Survival – Herskovits

In early 1974, Mr. Herskovits had x-rays performed at Group Health that disclosed infiltrate in the left lung.  Herskovits’ health continued to deteriorate, and Group Health made no further efforts to address these worsening symptoms.  In the spring of 1975, Herskovits sought a second opinion and was diagnosed with lung cancer. He died in March, 1977.  Irrespective of when the diagnosis was made, all parties agreed that Herskovits was likely going to die. If the diagnosis had been made in 1974 when Group Health should have made it, his chance of a 5 year survival was 39%.  By the time the cancer was ultimately diagnosed, his 5 year chance of survival had decreased to 25%. Thus, the delay in diagnosis may have reduced the chance of a 5-year survival by 14 %. The defense brought a motion for summary judgment arguing that the Plaintiff could not show that the delay in diagnosis more likely than not (51%) caused her husband’s death. The Court was asked to decide the question of whether a patient, with less than a 50 percent chance of survival, “has a cause of action against the hospital and its employees if they are negligent in diagnosing a lung cancer which reduces his chances of survival by 14 percent.” Id. at 611.

Holding: The Court rejected Group Health’s argument that plaintiffs must show that Herskovits “probably” would have had a 51 percent chance of survival if the hospital had not been negligent. It held that “medical testimony of a reduction of chance of survival from 39 percent to 25 percent is sufficient evidence to allow the proximate cause issue to go to the jury.” Id. at 619. The court articulated two different analyses:

  1. Justice Dore’s lead opinion discussed a substantial factor analysis: The medical error must be a “substantial factor” in causing the injury to seek damages, even when the lost chance attributable to the negligence is less than 50 percent.
  1. The Herskovitsplurality’s rationale espoused a proportionality approach: This theory, adopted by the Justice Pearson’s concurring opinion, holds that causation must be proven on a more probable than not basis. However, the lost chance determines the amount of damages, and is calculated as a percentage of total injury recoverable – a rationale of redefining the injury as “the lost chance.”

The court permitted an action for the negligent destruction of a less-than-probable chance of survival.

Concurring opinion: “A plaintiff ordinarily should be required to prove by the applicable standard of proof that the defendant caused the loss in question.

WHAT caused a loss, however, should be a separate question from what the NATURE AND EXTENT of the loss are”   recognize the loss of a less than even chance as an actionable injury. Therefore, I would hold that plaintiff has established a prima facie issue of proximate cause by producing testimony that defendant probably caused a substantial reduction in Mr. Herskovits’ chance of survival.

To illustrate, consider a patient who suffers a heart attack and dies as a result. Assume that the defendant physician negligently misdiagnosed the patient’s condition, but that the patient would have had only a 40% chance of survival even with a timely diagnosis and proper care.

Regardless of whether it could be said that the defendant caused the decedent’s death, he caused the loss of a chance, and that chance-interest should be completely redressed in its own right. Under the proposed rule, the plaintiff’s compensation for the loss of the victim’s chance of surviving the heart attack would be 40% of the compensable value of the victim’s life had he survived (including what his earning capacity would otherwise have been in the years following death). The value placed on the patient’s life would reflect such factors as his age, health, and earning potential, including the fact that he had suffered the heart attack and the assumption that he had survived it.


In this lost chance of survival claim, the patient died from a preexisting condition.  But the patient would likely have died from the condition anyway, even without the negligence of the health care provider. The provider’s negligence had the effect of reducing the patient’s chance of surviving the condition. It helps to visualize the facts of Herskovits on a graph as depicted below. The x-axis represents the percentage chance of surviving for 5 years. The y-axis represents time.

At point t0 below, Herskovits developed lung cancer. His health deteriorated (reflected by the blue line) until point t1, when he saw his doctor.

The cancer was improperly diagnosed, resulting in a continued reduction in the chance of survival. This continued until the patient’s death at t3.


Herskovitz original 1080p

However – if the cancer had been properly diagnosed earlier, Herskovits life would have likely been extended further. This is shown by the dotted blue line, ending at t4.

In other words, the failure to diagnose the cancer caused Herskovits to suffer a reduction in chance of survival quicker than if the cancer had been properly diagnosed.

So how do we calculate the loss of chance in this case?

The red triangle in the chart below represents the total value of Herskovits’ life, without any medical negligence.

Herskovitz original 1080p value of life with no negligence

The area under the curve below, from t1 to t3, shows the value of Herskovits’ life with the negligence.

Herskovitz original 1080p value of life because of the negligence

Finally, the last chart below shows the loss of chance, reflected by subtracting the quality of life with the negligence from the total quality of life. This shape under the curve represents the loss of chance Herskovits suffered.

Herskovitz original 1080p loss



In Mohr, the Washington Supreme Court had the opportunity to extend the lost chance doctrine to cases where the ultimate harm is some serious injury short of death. In a lost chance of a better outcome claim, the patient did not die, but instead the chance of a better outcome was reduced by the medical provider’s negligence.  Mohr, 172 Wn.2d at 857. In a traditional medical malpractice case, the negligence more likely than not (51%) caused a worse than expected outcome. Under a lost chance of a better outcome theory, the bad result was likely even without the health care provider’s negligence. The medical provider’s negligence simply made that bad outcome even more likely.

For example, in Mohr, Ms. Mohr alleged that her physicians had breached the recognized standard of care for treating head trauma, and that their negligence had substantially diminished her chance of a better medical outcome. Specifically, her medical experts opined that her stroke should have been diagnosed sooner, and that had she started anti-coagulants, anti-platelet agents, and general brain protection care earlier, she would have had a 50 to 60 percent chance of a better outcome – significantly less or even no disability.

The Washington Supreme Court concluded that, to the extent Ms. Mohr was able to prove that her physicians’ negligence reduced her chance of avoiding or minimizing her permanent disability, she was entitled to compensation for that lost chance of a better result. However, the court also concluded that Ms. Mohr’s damages would be limited to the “percentage” of the ultimate harm that she suffered that was attributable to her physicians’ negligence.

The Mohr court rejected Justice Dore’s approach of relaxing the causation standard and formally adopted the Herskovits plurality’s rationale of redefining the injury as “the lost chance.” Mohr,172 Wn.2d at 859.  A plaintiff must still present evidence that a defendant’s negligence was the “but for cause” of the plaintiff’s loss of chance. Herskovits, 99 Wn.2d at 634-35.  This loss of a chance is characterized as a compensable injury. Compensation awarded would be limited to that lost opportunity, as calculated via expert testimony. 

A plaintiff need not come forward with medical testimony that negligence of the provider was the likely cause of plaintiff’s death or bad outcome. But, a plaintiff must provide a physician’s opinion that the medical provider’s negligence “likely” caused a lost chance of survival or a lost chance of a better outcome. In addition, this opinion must articulate an actual percentage of a lost chance. Every Washington decision that permits a plaintiff to pursue lost chance contains testimony from an expert that includes an opinion as to the percentage or range of percentage reduction. See Herskovits,99 Wn.2d at 611 (14 percent reduction in chance of survival); Mohr, 172 Wn.2d at 849 (50 to 60 percent chance of better outcome); Shellenbarger, 101 Wn. App. at 348 (20 percent chance that the disease’s progress would have been slowed). A recent Washington unpublished decision found that without that percentage, the court would not be able to calculate damages, since the award is based upon the percentage of loss. See also, Smith v. Dep’t of Health & Hosps., 676 So.2d 543, 546-47 (La. 1996). Discounting damages by that percentage responds to a concern that the defendant would be held responsible for harm beyond that which it caused.

So again, the Mohr case is different from Herskovits primarily because the patient did not die. Instead, the patient suffered a loss of neurological function, beginning at t0. Doctors’ failure to properly treat Mohr when she first sought help at t1 caused her to suffer a continued decline of neurological function until t2. At that point, she was properly treated, continued to decline until t4, and then finally stabilized with substantially reduced neurological function.

Mohr original 1080p

 In this case, we can also evaluate what Mohr lost by looking at the area under the curve. The chart below shows the total value of Mohr’s life by mapping an area between the initial treatment, the stabilization of neurological function, and the best case scenario for treatment.

Mohr original 1080p difference

However, Mohr was not treated properly at t1. The next chart below shows the value of life with the negligence.

Mohr original 1080p lower curve

Like in Herskovits, we can illustrate the loss of chance by subtracting this area from the total value of life. This results in an area under the curve between t1 and t5 that reflects the loss of chance to improve and stabilize neurological function.

Mohr original 1080p difference


Loss of chance is an important concept in medical malpractice litigation and provides a relatively new theory of compensation and recovery that was previously denied injured plaintiffs.