- For example, cancer is probably the result of an accumulation within a given cell, of seven or so genetic changes, but the courts decide that any given cancer does not have a cumulative cause. The scientific probability of it not being cumulative in nature is very small indeed but the legal fact (following the Phurnacite case) is that it is not.
- For example, among those who make a claim for whiplash if 65% are actually injured and the test is 80% accurate then the Bayesian odds of making a diagnosis is six to one. The inference is that 86% will be diagnosed! Yet if a random sample of the population is assessed (annual prevalence ~ 1%), the odds are worse than eleven to one (against) that anyone given a whiplash diagnosis actually has such an injury. Given these scientific ‘facts’, the court would be forgiven for deciding either there was no such thing as whiplash or in the alternate, that everyone who makes a claim must be injured and it is for the defendant to prove they are not.
Science is not the decider of fact, it merely provides contextual information for fact finding.
Is there better use that can be made of scientific input?
First up is the erroneous design of science. Science is generally designed to test a hypothesis which makes sense in given theoretical framework. So in case of whiplash, scientists take subjects who are in perfect health and do unto them that which they will e.g. run into them from behind. Change in status is measured with varying degrees of success and opinions about causation are thus formed. But this approach and its subtending insights are fundamentally meaningless at common law. Unless the claimant can prove he was in perfect health prior to the alleged cause, then based on those experiments on those in perfect health, nothing of any merit can be said about his case. The courts need to hear about causation in tests of normal people, not perfect people. Fortunately, scientists do have the data required to adjust their findings to that end. Unfortunately, no-one has asked them to do it and those who have been told of the problem have done nothing as yet, to explore the effect!
Second is the use of the wrong statistical test. Theoretical frameworks, such as the provision of medical interventions, suggest which approach to statistics is to be adopted. A medic will optimise the sensitivity and specificity of diagnosis in order that medical care can be effective and yet not wasted on those with no injury. But this is not the right question at common law. In court the questions would be of two kinds illustrated by the following logical series 1) is the claimant probably now different from his pre-event state of health? 2) if so, does the difference have such a significance that he is harmed?
The first is a fact which can usefully be informed by scientific experts. Probabilistic tests of difference can be made. Given the right data, any scientist can calculate the probability that the claimant is now different from his factual baseline state. If the probability of difference is below 50% then he is not different and there is no case to answer. If greater than 50% then the question moves on to one of legal judgment as to the significance of that change.
Significance is a matter of legal opinion. In forming an opinion on this, the judge might take into account a measure of prognosis in similar cases, provided such studies were designed to answer the common law question, not a medical service provision question. He might take into account any measures of functional capacity, provided the right (factual) baseline was being compared with.
In short, just because a medic can justify the provision of a medical intervention doesn’t mean that the person is legally injured.
Far from it.
If you work through the maths, when a symptom is non-specific but relatively common, the medical diagnostic threshold is such that the probability of difference from normal might be as low as 20%. At common law this is not an injured person but in medicine the sensitivity and specificity are optimum.
In these cases, you would not ask a medic about diagnosis until the medic understood the question from a legal point of view.
For broken bones, the medical route to forming a view as to diagnosis is probably good enough for the common law.
Medical and common law views of diagnosis, cause, prognosis, degree of harm and the likely effect of medical intervention are fundamentally incompatible. They do however approximate to each other when the injury is severe and specific. In every other case, the medical view adds colour but is not the whole picture.
Fortunately, medical data can be converted into a form that actually advises the court in such cases.
Both of these points, design and statistical tests, have been explained to the Ministry of Justice ( whiplash consultation response), and the Transport Committee. All that needs to happen now is that they are evaluated, tested and tried in real cases. If nothing else, with these corrections, science will be able to provide advice leading to reproducible fact finding.