Medical-Legal Causation: Linking Your Injuries to the Crash
One of the quieter but more important questions in any injury claim is deceptively simple: is this particular treatment related to the crash? It matters because different insurance policies pay for different things. One coverage might apply if your care is related to a car accident, while a different coverage — or none at all — might apply if it is not. So somewhere along the way, someone has to decide whether the care you received is connected to the collision. That decision is what “medical-legal causation” is about.
Disclaimer: This post is intended for general informational purposes only and does not constitute legal advice. For guidance specific to your situation, please consult with a qualified personal injury attorney.
The Standard Is “More Probable Than Not”
Washington uses a “more probable than not” standard — meaning more than fifty percent likely. You do not have to rule out every other conceivable explanation for your symptoms.
A provider can acknowledge that a symptom could, in theory, have appeared on its own, and still reasonably conclude that it is related to the collision — as long as the crash is the more likely explanation. The existence of some other possibility does not defeat causation; what matters is which explanation is more probable.
Proximate Cause and the “But-For” Question
The law also speaks of “proximate cause” — a cause that, in a direct and unbroken sequence, produces the injury, and without which the injury would not have happened. A useful lens is the “but-for” question: but for the crash, would you need this care?
If you would not have needed treatment without the collision, but you do need it because of the collision, that generally points toward the care being crash-related. Keep in mind, though, that “but-for” is a helpful lens rather than the complete test, and a single injury can have more than one proximate cause.
Who Establishes the Connection
When causation, prognosis, or the need for treatment involves medical questions beyond ordinary experience, a qualified medical opinion is usually critical. That opinion is only as strong as the record it rests on, so careful documentation matters.
How that opinion reaches a decision-maker depends on the forum and the issues. It may be presented through live testimony, through a deposition, or through an admissible written report or declaration — Washington’s civil arbitration process, for instance, permits signed expert reports and declarations. In other words, connecting your injuries to a crash does not always require a treating provider to appear as a live witness.
A Common Myth: “Related Until the Benefits Ran Out”
A frequent error is the idea that care is crash-related only up to some arbitrary line — until the insurance benefits are exhausted, or until treatment is relabeled as “maintenance.” Coverage limits and labels do not determine what actually caused your need for care.
Take so-called maintenance care. The right question is not what it is called, but whether you would need this care in the absence of the collision. If someone has moved from active, curative treatment to ongoing symptom-relief care, and they would not need that care but for the crash, then it is still crash-related — even after the acute phase has passed, and even after a particular coverage has run out. You will also sometimes hear that care can only relate to a crash for a set number of years — but the connection does not expire on a calendar.
When a Later Event Enters the Picture
Sometimes something happens after the collision — a fall, a new incident — and the question becomes whether your later care is really about that new event. A truly independent later event that produces a different kind of injury can break the causal chain. That is called a superseding cause.
But a later event does not automatically become a superseding cause just because it happened afterward. Whether it genuinely interrupts the connection depends on things like whether it was a new and independent cause and whether it was foreseeable — often questions for a fact-finder rather than something an insurer decides unilaterally.
When Two Causes Overlap
Causation is not always all-or-nothing. Imagine someone with an open workers’-compensation claim for a back injury who is then in a collision that worsens that same back. Both the work injury and the crash may be proximate causes. When that happens, separating what the crash contributed is a fact-specific medical and legal question — multiple causes can genuinely coexist even when no one can assign a defensible percentage to each. That division, called apportionment, has its own logic, and we cover it in “Understanding Apportionment in Personal Injury Claims.” The key point here is that another contributing cause does not, by itself, mean the collision was not also a cause of the harm you are dealing with today.
Final Thoughts
Linking your injuries to a crash comes down to a practical standard: is it more probable than not that the collision is why you need this care? Labels, coverage limits, and later events all get raised — but the honest question is always whether you would need this treatment but for the crash.
Have questions about whether your treatment is being properly connected to your collision? Reach out to our team for a consultation. We are here to help injured people across Washington understand their claims and move forward with confidence.
