The work starts with the medical prognosis, because everything else follows from it. An expert in the relevant specialty reports on the injury and on how it is likely to develop. That view of the future is what allows the other experts to do their work. If the prognosis is unclear, the future losses cannot be valued properly.
Care is usually the next piece. A care expert assesses what you can and cannot do, and sets out what help is reasonably necessary as a result, expressed in hours per week. Where the need is permanent, the care package is costed over the rest of your life, which may bring in actuarial evidence on life expectancy. Treatment, equipment and accommodation are assessed in a similar way, each by the expert best placed to comment.
The financial losses are then calculated. An accountant examines what you earned, what you would probably have earned, and what you can now expect, taking account of your age, your occupation, your prospects and the state of the market. Where a pension has been affected, actuarial evidence follows. This is detailed work, and it is why the losses in a serious claim are set out one by one rather than lumped together.
Only when that picture is reasonably complete can the claim be valued and presented. Where the other side disputes the evidence, negotiations follow, and where agreement is not possible the case is decided by the court. Many serious claims settle through negotiation well before any hearing. Our page on serious injury solicitors explains how the whole claim is built around this work.