Article source: Loewy Law Firm
Proving that someone else caused your injury is only half the battle in a personal injury case. The other half, and the part that defendants fight hardest, is causation, meaning whether your specific injury came from the specific event at issue. Insurance adjusters and defense attorneys build arguments that your pain existed before, came from somewhere else, or was made worse by your own choices after the event, and the difference between winning and losing on causation frequently comes down to decisions made in the days and weeks after an injury.
Causation in a Personal Injury Case: What You’re Required to Prove
Liability and causation are separate hurdles. A defendant can be found negligent and still escape responsibility for your injuries if they can convince a jury that the negligence didn’t cause the harm you’re claiming.
In personal injury law, causation breaks down into two parts:
- Actual cause: The injury would not have happened without the defendant’s conduct. This is sometimes called the “but-for” test — but for what they did, you wouldn’t be hurt.
- Proximate cause: The injury was a foreseeable result of the defendant’s conduct, not something remote or far removed from what happened.
Both have to be established. A rear-end collision that sends you to the emergency room clears the actual cause bar easily. Where disputes arise is when the defense argues that your back pain, for example, was already there before the crash, or that your current condition has progressed far beyond what the crash could have caused.
How Defendants Build a Causation Dispute
Defense attorneys don’t wait until trial to start challenging causation. The process starts at the claim stage, and it’s built from your own records.
Pre-Existing Conditions as a Defense Weapon
A prior diagnosis of a herniated disc, arthritis, or degenerative joint disease gives the defense a starting point to argue that your pain predates the event. If your medical records show you saw a chiropractor or orthopedist in the two years before the crash, expect those records to be subpoenaed and used to argue continuity, meaning that your current condition is a continuation of what was already there.
What the defense can sometimes gloss over is the eggshell plaintiff doctrine, which holds that a defendant takes the victim as they find them. A pre-existing condition doesn’t relieve a defendant of liability for making that condition significantly worse. An aggravation of a prior injury is still a compensable injury. The distinction that an attorney will draw out is the difference between your baseline before the event and your condition after, and what caused that gap.
Treatment Gaps and What They Signal to the Defense
A gap in medical treatment, even a few weeks, gives adjusters room to argue that your injuries weren’t serious enough to require consistent care, or that something else caused a later flare-up. From the defense side, a gap is an invitation to introduce alternative explanations.
If you stopped treating after a few visits and then returned to a doctor months later with worsening symptoms, the defense will argue the two are unrelated. Your attorney will need medical evidence, typically from your treating physician, that the later symptoms are a continuation of the original injury rather than a new development.
Competing Medical Explanations
Defendants in personal injury cases can hire their own medical experts to examine you and review your records. An independent medical examination, or IME, sounds neutral, but it’s conducted by a physician selected and paid by the defense, and the resulting report is almost always favorable to the defense’s position.
IME doctors frequently attribute injury to degenerative changes, prior activities, obesity, age, or occupational strain rather than the event in question. Their reports are submitted as evidence, and without a credible counter from your treating physician or a retained expert, they can carry significant weight.
Medical Evidence That Establishes Causation
Not all medical documentation carries the same weight in a causation dispute. A diagnosis alone, without a clear statement connecting it to the event, gives the defense room to argue the injury came from somewhere else.
The most useful medical evidence for establishing causation includes:
- Treating physician notes that directly link the onset of symptoms to the event
- Imaging results, like MRIs or X-rays, taken close in time to the event that show acute injury rather than chronic degeneration
- Specialist referrals that trace back to the original treating physician’s records
- Consistent documentation of symptoms at each appointment, with no unexplained gaps
A treating physician’s opinion on causation carries more credibility than a retained expert’s, largely because the relationship is ongoing and the records reflect an actual clinical history. The problem is that physicians aren’t always trained to write records with litigation in mind. Phrases like “patient reports pain following a motor vehicle accident” are helpful, but what an attorney needs is a physician who can testify that, within a reasonable degree of medical probability, the injury was caused by the event.
Prior Treatment History: How It Can Hurt and Help Your Case
When Prior Records Work Against You
If you treated for the same body part or same complaints before the event, the defense will use those records to argue that your current condition isn’t new. Prior records showing lumbar complaints, for example, make it harder to argue that a crash caused your current lumbar injury, unless your attorney can demonstrate a clear change in severity or function.
Inconsistencies between what you told your doctors before the event and what you’re claiming now create additional vulnerabilities. Defense attorneys look for any gaps between your reported history and what appears in prior records.
When Prior Records Work in Your Favor
Prior records can strengthen your case if they show a healthy baseline before the event. A treatment history free of complaints for the affected body part, or records showing prior complaints resolved years before the event, gives your attorney a documented before-and-after to work with.
Records showing you had no prior complaints in the specific region now injured are something a treating physician can point to when explaining why the injury is attributable to the event rather than a pre-existing condition.
Expert Testimony in Causation Disputes
In contested causation cases, expert testimony frequently determines the outcome. A treating physician can testify about your care and their clinical observations, but a retained medical expert can offer a broader opinion about mechanism of injury and whether the event was capable of causing the type of injury you suffered.
The defense will put forward their own expert, usually the IME physician, to offer a contrary opinion. Jurors are then asked to weigh competing expert testimony, which is why the credibility and qualifications of each expert, and the strength of the underlying records, carry so much weight.
Causation disputes around traumatic brain injury, spinal cord damage, or psychological injury routinely produce sharply conflicting expert opinions, and the side with more complete medical records and a treating physician who consistently documented symptoms and their strong possible relation to the event is in a better position to prevail.
Protecting the Causation Argument
Causation disputes aren’t created at trial. They’re built gradually by the defense using gaps and inconsistencies in your records and behavior after an injury. A few practical steps can limit the ammunition available to the defense:
- Seek medical attention as soon as possible after an injury and follow through with every recommended appointment
- Tell your doctor exactly what happened and exactly what hurts, and be consistent at every visit
- Don’t give recorded statements to an insurance adjuster before speaking with an attorney, since those statements can be used to create contradictions with later medical records
- Keep a written log of your symptoms, how they change over time, and how the injury affects your daily life
- Disclose your full medical history to your attorney so prior records don’t surface as a surprise during litigation
Causation at Trial
When causation goes to a jury, you have to prove by a preponderance of the evidence (meaning more likely than not) that the defendant’s conduct caused your injury, which is a lower bar than in criminal cases but still requires documented, credible evidence connecting your injury to the event.
How Juries Evaluate a Causation Dispute
Jurors usually evaluate causation by looking at the full picture your records paint:
- Consistency of your medical treatment from the date of injury forward
- Whether your treating physician directly linked your injury to the event in their notes or testimony
- Documented gaps in treatment and whether they were explained
- Your prior treatment history for the same area of the body
- The credibility of expert witnesses on both sides
Where Cases Are Won and Lost on Causation
Juries tend to follow the records, and a consistent treatment record with a physician who can testify to causation within a reasonable degree of medical probability is difficult for the defense to overcome. Cases that fare well on causation typically share the same characteristics:
- No prior treatment for the same area of the body, or a documented gap of years before the event
- A treating physician whose notes link symptoms to the event from the first visit forward
- No unexplained breaks in treatment after the injury
- Expert testimony that aligns with and supports the treating physician’s conclusions
Treatment gaps, prior complaints in the same area, and no physician opinion directly connecting your injury to the event give the defense room to introduce doubt — and juries can find for defendants on causation even when liability is not seriously contested. Causation disputes are decided by the quality of the medical record built in the weeks and months after an injury, and an attorney brought in before those records are complete can help identify gaps before they become permanent.
