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What is an inevitable Accident?

How many of us have been in a motor vehicle accident or witnessed such an event and had the thought that an accident simply would have happened regardless of what the parties had done?

Have you ever wondered how those types of accidents are sorted out in the legal system?

Determining liability for accidents in this category can be tricky. For example, who is liable when there are such factors contributing to an accident such as potholes, flooding, black ice and other external factors, such as weather? When are drivers expected to be aware of those additional hazards and when do those external factors make an accident “inevitable” or unavoidable?

This post is intended to provide some basic information about a defense to such accidents which exists under Canadian law. While this article is not an exhaustive discussion of the topic, it is designed to provide some general information as to a helpful defense that is out there in terms of automobile accidents that seem to have been unpreventable.

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What is the “inevitable accident” doctrine?

The doctrine of the “inevitable accident” is a defense to automobile accidents under Canadian law when the accident is deemed to have been inevitable or in other words, not preventable. There are generally two different types of situations where the “inevitable accident” doctrine is used.

The first type of instance is when an accident is inevitable because it was not caused by anyone’s negligence but could not be anticipated or prevented by the exercise of reasonable care. In other words, it was caused by factors beyond anyone’s control and therefore no one would be liable based upon a negligence theory because the accident was not foreseeable.

The other instance where the inevitable accident defense might be available is when the primary cause of the accident was an internal issue to the driver or their vehicle, such as a medical condition or an equipment failure.

See also: Is the Driver of the Rear Vehicle Always Responsible for a Rear-End Accident in Ontario?

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When can the “inevitable accident” defense be used?

In order for a plaintiff to be successful on a personal injury claim involving an automobile accident, the plaintiff must generally prove that the negligence, or failure to exercise reasonable care, of another party, was the cause for their loss or damage.

A defendant may use the “inevitable accident” defense to prove that the accident could not have been avoided, despite the exercise of reasonable care. So what exactly does a defendant need to prove to successfully use the inevitable accident defense?

Generally speaking, the defendant must prove that the accident could not have been avoided despite driving with reasonable care and diligence. As mentioned above, this type of defense could be used in cases involving situations such as black ice, potholes and other similar instances including animals darting into the roadway, mechanical failures and weather conditions.

In addition, it could also be used sometimes in cases involving sudden medical conditions. There are clearly some instances where there are factors that are legitimately beyond the control of a driver but that may vary significantly based upon the facts and circumstances of a particular case. Some examples of both of these instances are included below:

Medical Condition – Inevitable Accident Defense

Often an accident will be caused by someone having a seizure, a heart attack or other emergent medical condition that is a significant contributing factor to the accident. The determining factor in cases involving a sudden medical condition as to whether someone can use the inevitable accident defense in the case of a medical condition is whether the medical condition might have been foreseeable based upon past health history.

For example, someone who has never had a heart attack or any previous medical history involving a heart condition would be much more likely to be able to successfully use the “inevitable accident” defense for an accident than someone who had a known health history with a particular medical condition. One example of this might be an individual with epilepsy who has had previous seizures while driving. It is much more difficult for this person to successfully argue that their medical condition was not foreseeable given this previous health history.

See also: Does My Auto Accident Injury Qualify as a “Permanent Impairment”?

There have been cases decided on both sides of this defense when it comes to medical history but the driving force behind whether a defendant can successfully use the defense is typically whether there was some type of prior knowledge of a medical condition or preventive measures that could have been taken in connection with that condition which might have avoided the accident all together. Thus, in the case of accidents related to medical conditions, it is much more of a mixed bag.

Mechanical Defect or Failure

In general, a defendant in a motor vehicle accident who is relying on the inevitable accident doctrine in connection with a mechanical failure will have to establish that the failure could not have been prevented or discovered with reasonable inspection or maintenance of the vehicle.

An example of this would be if a vehicle’s brakes failed unexpectedly and there had been no prior indication that the brakes might fail, such as routine maintenance that recommended replacement of the brakes or any outward indication that they were not working (for example, how the brakes sounded when the vehicle was operated)

Although this defense can be helpful as mentioned above, there is still a relatively heavy burden on a defendant to prove that there was really no way for the defendant to eliminate any risks that contributed to the accident and/or to respond to conditions that contributed to the accident.

In other words, there must really be a truly unforeseeable series of events that occurs in order for a defendant to successfully use this defense, and no ability for the defendant to take any action to mitigate the circumstances.


The inevitable accident doctrine can be a very helpful defense for drivers who are involved in those truly unusual circumstances that are unforeseeable and unpreventable. However, whether a driver is able to successfully avoid liability using this defense will depend on the facts and circumstances of the particular case. The key question will always be whether the driver could have adjusted his or her driving to avoid the accident completely. If there was no adjustment the driver could have made, then the inevitable accident doctrine may provide a successful defense for a defendant.

However, if the driver had options within his or her power to adjust his or her driving, react, or otherwise mitigate the circumstances, that defense will not be available. The best policy is obviously to always drive with the utmost caution and do everything within one’s power to mitigate those risks that are foreseeable. However, sometimes that isn’t the case and hence the reason that the inevitable accident doctrine exists.

If you’ve been involved in a motor vehicle accident and need help navigating the associated legal hurdles, get in touch with one of our lawyers for help.

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