The High Court has refused an insurer permission to rely on a new expert whose evidence reduced the estimated life expectancy of a personal injury claimant.

The defendant in Chaplin v Ben Pistol Allianz Insurance plc had sought to introduce the evidence of statistics specialist Professor David Strauss, in a case where two experts had already submitted their joint report.

Mr Justice Jay ruled that the insurer had failed to show a relevant and sufficient change in circumstances that would allow for this evidence to be admitted four months before trial.

He agreed that any adjournment of the trial date – made likely by admitting new evidence – would be ‘intolerable’ for the claimant’s family. He rejected Allianz’s argument that the claimant would have little option but to accept the Strauss evidence as authoritative and reliable, adding: ‘Assuming that new data were provided, the claimant would be entitled to have it subjected to appropriate scrutiny by an expert in medical statistics; it would not have to be taken as Gospel.

The court heard that the dispute came as part of a claim by the victim of an RTA who suffered a severe traumatic brain injury and is wholly dependent on others for his care needs.

It was accepted his life expectancy has been significantly reduced, and the parties’ existing experts were ‘not far apart’ on by how much. In contrast, the issue of the Strauss evidence was worth a seven-figure sum to the parties, the court heard.

The defendant argued that statistical evidence was capable of providing greater certainty about the claimant’s case. It was submitted that both existing experts had both over-estimated his life expectancy, having suggested he would live between 30% and 44% of normal. Instead, Strauss’ method provided the best database and was the best guide for the estimation of life expectancy, which was reduced to 27%.

The judge said that a large measure of consensus achieved by the neurological experts would have been ‘fundamentally and radically upset’ by the admission of new evidence.

He added that while evidence from a medical statistician was, in principle, admissible it should be seen as the starting-point for clinical judgements made by medical witnesses.

The judge added: ‘Medical experts are usually well able to apply and interpret quite complex statistical evidence which can be admitted as hearsay (particularly if set out in a published paper which has been peer-reviewed) without the need to call probative or explanatory evidence.’