Causation: Basic Principles in Medical Negligence

doctor filling out patient records

Medical negligence cases present a myriad of inherent complexities and challenges for the plaintiff. One of the essential elements a plaintiff must establish is causation. Causation is the direct relationship between the defendant’s negligence and the injury to the plaintiff. The question that must be answered is: Did the defendant’s breach of the standard of care cause or contribute to the plaintiff’s injuries? There must be a substantial connection between the plaintiff’s injuries and the defendant’s negligence. Establishing causation is the responsibility of the plaintiff. If causation is not established, meaning the plaintiff fails to demonstrate that their injuries on a balance of probabilities were, partially or entirely a result of the medical professional’s negligence, there will be no compensation for the plaintiff.

Establishing causation in medical negligence cases is particularly difficult and complicated. Issues relating to pre-existing and underlying conditions, inherent procedural risks, and known post-operative complications can serve to muddy the facts of a plaintiff’s case and make building a definitive causal link between the physician’s negligence and the plaintiff’s injuries hard to do. The lawyers representing the plaintiff in a medical malpractice case will spend a significant amount of time, effort, and money to establish causation.

Legal Tests Used to Establish Causation

The “but for” test is a critical test the plaintiff must satisfy in order to prove their case. The plaintiff must be able to prove that, on a balance of probabilities, “but for” the defendant’s negligence, they would not have sustained their injury. Thus, the defendant’s negligence caused the plaintiff’s injury. While this test may seem reasonable and simple, in some cases it is very difficult for the plaintiff to apply it and prove causation in their case. Variables like potential multiple contributing factors, the presence of multiple defendants, and a plaintiff’s past medical history can serve to complicate the application of the “but for” test in a plaintiff’s attempt to establish the causation element.

Again, medical negligence cases present their own unique challenges in applying the “but for” test. Inherent complexities in the medical field make the challenge of examining and drawing conclusions from expert evidence particularly difficult and necessitate the need for an alternative test. In some cases, the medical evidence presented by scientists and doctors seems to contradict common sense and past experience. In some cases, the courts have relied upon other tests like the “material contribution” test to help determine whether or not the defendant was negligent and caused the plaintiff’s injuries. The material contribution test establishes causation when it can be determined that the defendant’s negligence materially contributed to the plaintiff’s injury. The material contribution test acknowledges other variables presented by things like the person’s health before the incident in question and simply asks whether or not the defendant was part of the cause of the plaintiff’s injury. The defendant will be liable for all of the plaintiff’s injuries their negligence caused or contributed to. The “material contribution” test can only be substituted for the “but for” test in very rare, exceptional circumstances. In fact, it can only be used when it is impossible to establish causation by using the “but for” test. First, it may be applied in cases where it is impossible for the plaintiff to establish causation by utilizing the “but for” test due to factors uncontrollable by the plaintiff. Additionally, it may be applied when the defendant owed a duty of care that they then breached and as a result of that negligence, exposed the plaintiff to an unreasonable risk of injury that the plaintiff then sustained.

The Evolution of Causation in Canadian Courts

The issue of causation is one Canadian courts have examined for decades. They have considered elements like who the burden of proof rests upon and what the burden should be. In the 1990 Snell v. Farrell decision made by the Supreme Court of Canada, the court addressed the issue of causation:

“Dissatisfaction with the traditional approach to causation stems to a large extent from its too rigid application in many cases. Causation need not be determined with scientific precision. In many malpractice cases, the facts lie particularly within the knowledge of the defendant, and very little affirmative evidence on the part of the plaintiff will justify the drawing of an inference of causation in the absence of evidence to the contrary.  It is not strictly accurate to speak of the burden of proof shifting to the defendant when what is meant is that evidence adduced by the plaintiff may result in an inference being drawn adverse to the defendant. The legal or ultimate burden remains with the plaintiff, but in the absence of evidence to the contrary adduced by the defendant an inference of causation may be drawn although positive or scientific proof of causation has not been adduced. If some evidence to the contrary is adduced by the defendant, the trial judge should weigh that evidence according to the proof. It is therefore not essential that the medical experts provide a firm opinion supporting the plaintiff’s theory of causation.  Medical experts ordinarily determine causation in terms of certainties whereas a lesser standard is demanded by the law. It is the function of the trier of fact, not the medical witnesses, to make a legal determination of the question of causation.”

In this medical negligence case, neither side was able to establish causation or lack thereof with any certainty. The trial judge ruled in favour of the plaintiff, asserting that because the defendant had, through their negligence, created a risk of injury and the injury that the plaintiff sustained fell within the possible injuries the defendant may have caused, the defendant was liable. The court held that the defendant had not, in this case, disproved causation. This case served as a catalyst to further examine the requirements of causation in Canadian courts. At the heart of the debate was the issue of the utilization of common-sense reasoning in determining causation.

Over two decades later, in another negligence case involving a motor vehicle accident, the Supreme Court of Canada again directly addressed the issue of causation. The trial judge employed the material contribution test in their ruling. The case was appealed and eventually made it to the Supreme Court of Canada. There the central question was whether or not it was appropriate to apply the “material contribution” test in this case. The court held that the “material contribution” test should not have been applied and was insufficient to establish causation. That decision firmly established the “but for” test as the central means by which to establish causation in negligence cases. The decision also addressed the issue of the need for definitive scientific evidence. The Court held that a judge could use a broad, common-sense approach when applying the “but for” test and should be allowed to infer causation on a balance of probabilities.

The Problem Presented by Multiples

Modern medicine is incredibly complex and thus cases involving negligence committed in this area are often layered and nuanced. Further complicating many medical negligence cases are issues like multiple parties in a case, multiple errors that were committed, multiple contributing factors that may have played a role in the outcome, and multiple causes for the plaintiff’s injuries.

  • Multiple Parties: In some medical negligence, the plaintiff names multiple defendants. This may include a variety of medical professionals who participated in their treatment like multiple specialists, surgeons, nurses, technicians, or pharmacists. These cases make it particularly difficult to establish causation because while it may be possible to determine that a defendant caused the plaintiff’s injuries, it’s much more difficult to determine which one.
  • Multiple Errors: In cases where a plaintiff was the victim of multiple errors committed by multiple medical professionals, the aim of their legal team will be in trying to determine which error actually caused the injury.
  • Multiple contributing factors and multiple causes: There are a litany of factors that play a critical role in determining our overall health, susceptibility to injury or disease, and ability to recover from injury or treatment. When a patient is harmed after medical treatment, there could be multiple explanations for why the treatment was unsuccessful and why they sustained an injury. Pre-existing medical conditions and a plaintiff’s overall poor health can play an important role in medical negligence cases. They allow a defence team to point to other probable causes for a plaintiff’s injury, thus making the plaintiff’s attempt to establish a causal link between the defendant’s negligence and their injury even more difficult.

The Importance of Medical Experts in Medical Negligence Cases

Medical experts are an essential element in medical negligence cases. Expert opinion evidence will help the court determine who was at fault, whether or not causation has been established, and ultimately, what the proper conclusion is. Experts must only provide opinion evidence that falls within the scope of their expertise. For example, an expert neurosurgeon will supply opinion evidence related to the field of neurosurgery. Medical experts used in medical negligence cases may include:

  • Psychiatrists
  • Neonatologists
  • Obstetricians
  • Chiropractors
  • Pharmacists
  • Immunologists
  • Anesthesiologists
  • Cardiologists
  • Dermatologists
  • Infectious disease specialists
  • Orthopedic surgeons

Experts provide valuable opinion to the court on issues such as risks of treatment, the timing of an injury, the significance of other contributing factors, analysis of testing data, and other potential causes for the plaintiff’s injury. Experts will assist the court in navigating the medical evidence presented by both the plaintiff and the defence.

Have You or a Loved One Been Harmed by Medical Malpractice?

Klein Lawyers handles medical malpractice cases, has a stellar reputation, and has an outstanding track record. We understand how to identify instances of malpractice where diagnostic errors and other forms of medical negligence have harmed innocent victims. We have the resources, knowledge, and experience Canadians need to get the justice and compensation they deserve.

We will start by conducting an in-depth investigation of the evidence in your case. We will take the time to really listen to your story, obtain and review any needed records, and thoroughly evaluate your potential claim. During the case, we will retain key medical experts to establish the critical details of the injury that occurred. We strive to make this process as easy for you as possible, shouldering as much weight as we can. Our aim is that you focus on your life, while we focus on your case.

We keep you informed throughout the entire case so you never feel like you are in the dark. We want you to understand what’s going on and feel comfortable asking any questions along the way. Too often, we hear concerns expressed from potential clients about what the process will be like, what they will need to do, how often they will hear from their lawyers, and what will be expected of them. We will make it clear right from the start. You will know what to expect, and we will stay true to our commitment to you. Communication and transparency are important to our team, and you will recognize that as our client.

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Klein Lawyers has over 20 years of success and experience in the legal field. During that time, we’ve worked hard to earn the trust and respect of Canadians who need legal representation. Working with an experienced lawyer is critical, and our team understands the trust clients place in us when representing them. We value that trust and feel honoured that so many clients choose our law firm to fight for them. We are passionate about obtaining the best possible outcome for our clients. While we know it is never easy, we will not stop standing up to medical professionals who harm individuals through their negligence.

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