The real issue is not whether a claimant had problems before the accident. It is whether the accident caused additional injury, aggravated an existing condition, or accelerated a process that was already underway. That distinction sits at the heart of many Medico-legal disputes.
The law starts from a relatively straightforward position. A defendant generally takes the claimant as they find them. The so-called “eggshell skull” principle means that a person’s underlying vulnerability does not relieve a wrongdoer of responsibility simply because the consequences proved more severe than might have been expected in an otherwise healthy individual. In practice, however, Medico-legal assessment rarely ends there.
Medical experts are not asked merely whether an accident happened. They are asked to separate the effects of that accident from everything that came before it. That task becomes progressively harder as the claimant’s medical history becomes more complex. Sometimes the analysis is relatively uncomplicated. A claimant may have suffered a whiplash injury years earlier, made a full recovery, and remained symptom-free until the index accident. Where the evidence supports that chronology, the previous injury may carry little significance. The expert may conclude that the claimant sustained a fresh injury with its own prognosis and recovery period.
These cases are rarely controversial, the greater challenge arises when symptoms were already present before the collision.
A claimant who attended their GP repeatedly for neck pain before an accident presents a different evidential picture from somebody who had enjoyed years of complete recovery. The expert must establish a baseline. How severe were the symptoms? How frequently did they occur? Was treatment being sought? Were employment, hobbies, or daily activities already affected? Only after establishing that baseline can the expert begin to assess what changed.
The central question becomes one of aggravation. Did the collision materially worsen the claimant’s condition? If so, by how much and for how long?
This is where compensation disputes often become focused. The claimant may experience genuine symptoms after the accident, but not every symptom will necessarily be attributable to the accident itself. Equally, the existence of a pre-accident condition does not mean the accident played no meaningful role.
Both extremes can produce unreliable conclusions.
Another common scenario involves acceleration rather than aggravation. An individual may have mild degenerative changes or intermittent symptoms that were expected to remain manageable for years. Following a collision, those symptoms become persistent, more severe, or functionally limiting.
In such cases, the expert may conclude that the accident accelerated a process.
