The Medical Expert Opinion in a Disability Claim
In personal injury matters the decisive question is medical, and the court decides on the basis of expert opinions. This guide explains what separates the four kinds of medical assessment, why a disability percentage from one forum does not carry automatically to another, and what a sound opinion must contain.
Why the expert opinion is the central document
In personal injury matters the decisive question is almost always medical rather than legal: what exactly was affected, to what degree, and whether it results from the event relied on.
The court does not determine that itself. It decides on the basis of medical expert opinions, and at times appoints an expert of its own. The quality of the opinion therefore shapes the outcome more than any legal argument, and the gap between the parties is almost always a gap between opinions rather than between facts.
The same logic applies outside court: the National Insurance Institute, insurers and pension funds all base their decisions on a medical assessment, each under its own rules.
Four kinds of assessment, and how they differ
- Treating doctor's records. The factual basis. They document what happened and what was found, but they are not an expert opinion: they do not determine a degree of disability and do not analyse causation.
- A party's expert opinion. Prepared at the request of the claimant or the defendant by a specialist in the relevant field, and intended to serve as evidence.
- A court appointed expert. Appointed where the opinions conflict. Those findings materially affect the outcome.
- A medical board. Operates before the National Insurance Institute under that body's own rules, not under tort law.
All four concern the same body, but ask different questions and apply different criteria.
Why a disability percentage from one forum does not carry to another
This is the most common point of confusion. A person receives a disability percentage from one body and assumes the figure transfers automatically to every other process. It does not.
The reason is that each framework examines a different question under its own rules. An assessment made for benefit purposes rests on that framework's rules; a tort claim examines the loss caused and its causal link to the event; and a private policy is construed according to its own wording.
An assessment obtained in one forum is therefore important evidence but not decisive in another, and at times it does not address the same question at all. Planning the order in which the routes are pursued is part of the work, not a technicality.
What a sound opinion must contain
- The full factual background, based on the medical file rather than an oral account.
- Examination findings made by the expert personally.
- A reasoned diagnosis, referring to the documents it rests on.
- A determination of the disability percentage, citing the provision under which it was set, and distinguishing temporary from permanent.
- An analysis of causation between the event and the injury, and where necessary an apportionment between a pre-existing condition and its aggravation.
- A view of the future: further treatment required, the prospect of deterioration, and the effect on function.
An opinion that does not analyse causation, or does not distinguish a pre-existing condition from its aggravation, will meet those exact points from the other side.
Medical disability is not loss of earning capacity
Two terms that sound similar and measure entirely different things.
Medical disability describes the injury to the body. Impairment of earning capacity describes the effect on the ability to work and earn, and depends on age, occupation, education and the nature of the work.
The very same disability may change the life of someone in physical work and barely affect someone working at a desk. In personal injury matters this is usually the main gap between the parties, so an opinion that addresses only percentages and not functional effect leaves the most important part unanswered.
How the expert is chosen
- From precisely the right field. An expert from an adjacent specialty is weakened against one from the exact field in which the treatment was given or the injury caused.
- With experience in writing opinions. An excellent clinician does not necessarily write an opinion that withstands cross-examination.
- Given a complete file. An opinion written on partial records will fall on that point.
The choice follows the nature of the injury rather than convenience, and where the injury crosses fields more than one opinion is sometimes required.
Three mistakes that recur
- Proceeding on the treating doctor's records alone. They are the basis, but they are not an opinion and do not determine percentages or causation.
- Assuming a percentage from one body transfers to another. Each framework examines a different question under its own rules.
- Ignoring a pre-existing condition. It is better for the opinion to address it and apportion between the prior state and the aggravation than to let the other side raise it first.
In summary
The medical expert opinion decides the fate of a personal injury claim, because the central question in it is medical rather than legal. The treating doctor's records are the factual basis but are not an opinion; a party's opinion is intended as evidence; and a court expert is appointed where the opinions conflict. A disability percentage set in one framework does not carry automatically to another, because each examines a different question under its own rules. Above all, medical disability and impairment of earning capacity are two different things.
The complexity here is not in obtaining a document but in building it: choosing the right expert, putting a complete medical file before them, and ensuring the opinion addresses causation, any pre-existing condition, and the functional effect. That work calls for familiarity with how each framework assesses matters, and for professional legal representation by a lawyer practising in the field.
If you are approaching a disability or personal injury claim, contact us and we will consider together which opinions are needed and in what order.
Frequently asked
I was given a disability percentage by one body. Does it apply to my claim?
Are the treating doctor’s records enough?
How is an expert chosen?
I have a pre-existing condition. Does that defeat the claim?
What is the difference between medical disability and loss of earning capacity?
What must appear in the opinion?
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