The cost of clinical negligence claims continues to rise, despite efforts to reduce this now ageing burden to the National Health Service (NHS) in England. From a welfarist perspective, reforms are needed to reduce avoidable harm to patients and to settle claims fairly for both claimants and society. Uncertainty in the estimation of quanta of damages, better known as financial settlements, is an important yet poorly characterised driver of societal outcomes. This reflects wider limitations to evidence informing clinical negligence policy, which has been discussed in recent literature. There is an acute need for practicable, evidence-based solutions that address clinical negligence issues, and these should complement long-standing efforts to improve patient safety. Using 15 claim cases from one NHS Trust between 2004 and 2016, the quality of evidence informing claims was appraised using methods from evidence-based medicine. Most of the evidence informing clinical negligence claims was found to be the lowest quality possible (expert opinion). The extent to which the quality of evidence represents a normative deviance from scientific standards is discussed. To address concerns about the level of uncertainty involved in deriving quanta, we provide five recommendations for medico-legal stakeholders that are designed to reduce avoidable bias and correct potential market failures.