Medical Malpractice

Medical Malpractice Series, Part 2 - What is "Causation"?

Jan Marin
Senior Associate, Gluckstein Lawyers

Haven’t read part one of our Medical Malpractice Series, click here to read it!

How Causation is Defined

In medical negligence cases there are two things that need to be proven in order to succeed:  

  1. That a health care provider breached the standard of care and;
  1. That this breach caused an injury.  

Causation may seem simple—did one event cause another? In reality, it can be an incredibly complex area of the law.

The purpose of this blog is to give readers, and those considering a medical negligence lawsuit, an introduction to “causation” and explain how courts and lawyers determine it. Causation is determined by the specific facts in a case. Even very similar cases can have very different determinations on causation.  

Examples of Determining Causation

How is causation determined if a family doctor fails to order a test (or loses track of a result) which could have resulted in detection of cancer? Perhaps an earlier detection of the cancer would have led to a better outcome, but it is also possible that earlier detection would not have stopped the cancer from progressing.

Another example – what if a nurse fails to report significant changes in vital signs and blood oxygen levels to the doctors, and the patient dies of a pulmonary embolism? Seems straight forward, but what if that patient was already dying and may have likely died in a week anyway? What if the blood clots were in a location which makes their removal/treatment difficult? These are a couple of examples, which demonstrate why causation can be so difficult.  

The Importance of Medical Experts

As discussed in part one of this series, medical experts are crucial for medical malpractice cases to succeed.

In the above examples, the first expert a claimant would speak to would not be a standard of care expert (i.e. a family doctor or nurse). The claimant would want to understand the underlying condition first.

For example, in the family doctor case, the claimant would need to know about the stage and type of cancer and the likelihood of a good outcome if it were identified earlier. They would then discuss this with an oncologist. If the answer is that the cancer is aggressive and treatment unlikely to succeed, it doesn’t matter if there was an error by the family doctor.

In the case with the nurse, if the patient was likely to pass away soon in any event, the error may have resulted in death occurring a few days earlier and the damages would be very limited. If the clot were not treatable then failure to detect it would not result in a successful case due to causation.

These kinds of situations are the difficult reality in medical negligence cases. Surely, you may be thinking – “that doesn’t seem fair”. Unfortunately, the law is clear; even if there is a breach of the standard of care, there would not be any compensation if it did not cause the injury.  

Multiple Health Care Providers, Multiple Mistakes, Multiple Causes

Due to the complex nature of the human body, our health and well-being is influenced by many factors. This means that an injury or disease can often be explained by more than one possibility for what caused the problem. This includes the possibility that a mistake was made by more than one healthcare provider.  

For this reason, it is important to sue the right person (or people) to ensure that your case is successful. The team of lawyers and medical experts working on your case would have to look at all of those involved to ensure that you are suing the right parties. Often, there are things in the medical records that clients don’t even know occurred, or had no idea demonstrated poor care.  

On many occasions, the healthcare provider(s) and their lawyers suggest that the injury was caused by something other than a mistake. This, in many cases, includes arguments that the injury is related to pre-existing issues, such as the reason you were attending the hospital in the first place, other underlying health conditions, or a genetic condition.  

Legal Causation

Causation is determined by applying the “but for” test, which means that “but for” the healthcare provider’s negligence, the injury would not have occurred. Unlike the criminal cases, where things are determined beyond a reasonable doubt, the legal components of a medical malpractice case are determined on a balance of probabilities. This means you must prove that it is likely the injury would not have occurred ‘but for’ the healthcare practitioner’s negligence. Causation is a complex area of the law and in most cases would benefit from the expertise of a lawyer.

Every Case is Fact Dependent

As mentioned above, the causation analysis is completely fact specific. After reviewing all the details and conducting a thorough investigation, a medical malpractice lawyer would be able to determine if your case has merit. If they find that a breach in the standard of care occurred and that your injuries were likely caused by the breach, you’ll be better equipped to decide if you want to proceed with a lawsuit.

Jan Marin is a Medical Malpractice and Professional Liability Lawyer with Gluckstein Lawyers in Toronto, Ontario, Canada.  Jan received her Bachelor of Arts (Honours) in Development Studies at Western University in London, Ontario, Canada and her Juris Doctor degree from Western’s Law School in 2009.

Jan can be reached at:



jan marin medical malpractice lawyer gluckstein painworth personal injury
Jan Marin, Gluckstein Lawyers

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