LNCtips.com:  Pyramiding of Inferences

As you know, an inference is a sensible conclusion based on both evidence and speculation. For example, if you go to a friend's house and it smells like cabbage, you might infer that your friend had cooked or eaten cabbage in her home. Pyramiding of inferences (also called stacking of inferences) is an evidentiary rule that prohibits one from stacking one inference upon another to come to a conclusion. Whether you're an independent, in-house, or expert legal nurse consultant, you need to be able to recognize pyramided inferences.

Some (but not all) states restrict pyramiding of inferences in civil litigation. Let's look at an example of this concept. A 62-year-old male patient visits his primary care provider (PCP) and learns that his blood pressure is 200/100. The PCP prescribes a medication for the blood pressure, refers the patient to a specific cardiologist, gives him the name and phone number of the cardiologist, and instructs the patient to return in one week. The patient returns to the PCP's office one week later and learns that his blood pressure is 170/99. The patient has filled the prescription but has not made an appointment with the cardiologist because the patient thought the PCP was going to make it for him. Because of the misunderstanding, the PCP asks his appointment clerk to contact the cardiologist. The clerk obtains an appointment for the patient for the next day due to a cancellation of one of the cardiologist's patients. Unfortunately, the patient dies in his sleep that night. The medical examiner lists the cause of death as cardiac arrhythmia. The wife wants to file a wrongful death and//or medical malpractice lawsuit against the patient's PCP. Below is a summary of her reasoning.

If the PCP had made the appointment for the cardiologist at the patient's first visit, the cardiologist would have seen before the cardiac arrhythmia occurred.

If the patient had gone to the cardiologist, the cardiologist would have diagnosed the cardiac arrhythmia.

If the cardiac arrhythmia had been diagnosed, the cardiologist would have been able to prevent it.

If the cardiologist had prevented the arrhythmia, her husband would still be alive.

As you can see, there are four inferences in this case. The first inference is the basis for the second inference, the second inference is the basis for the third inference, and the third inference is the basis for the fourth inference. Each inference assumes that the earlier inference is true; this is where the stacking or pyramiding comes in. However, a defense attorney could easily argue that at least some of the inferences contain more speculation than evidence. For example, the cardiologist may have needed to do extensive testing before making a diagnosis. There's also no guarantee that the cardiologist could have taken action immediately to prevent the cardiac arrhythmia.

What does this mean for legal nurse consultants? All LNCs need to know if their state permits stacking of inferences. Unfortunately, I was unable to find a list defining which states do and don't permit it. However, typing the state name and keywords of "pyramiding," "stacking," "inferences," and "medical malpractice" will identify whether there is case law for that state. LNCs also need to identify stacked inferences and bring them to the attention of the attorney. Expert LNCs need to ensure that all inferences are reasonable. And, of course, if the expert LNC's case is in a state that doesn't permit pyramiding of inferences, the expert can't use stacked inferences.

...Katy Jones