Part 6 – Expert Witnesses Don’t Lose Credibility in Court. They Lose It Months Earlier.
Throughout my previous articles I have considered a number of the professional disciplines that underpin effective expert evidence, including transparency in the use of assistants, maintaining independence, the duty to investigate rather than simply accept instructions and the importance of remaining willing to reconsider an opinion as the evidential picture develops. Those principles are not isolated obligations. They are all directed towards a single objective: establishing and maintaining the credibility of the Expert Witness.
There is, however, one aspect of expert evidence which I believe is frequently misunderstood. Popular perception often suggests that an Expert Witness succeeds or fails in the witness box; that credibility is won through confident answers under cross-examination and lost when an advocate exposes weaknesses before the Court. Whilst skilled cross-examination undoubtedly has the ability to reveal deficiencies in expert evidence, I respectfully suggest that it rarely creates them. More often than not, the weaknesses exposed at trial have existed for many months. They were simply waiting to be identified.
The credibility of an Expert Witness is established long before any hearing takes place. It begins from the moment instructions are accepted. The questions an expert asks at the outset of an appointment, the scope of the investigations undertaken, the documents requested, the assumptions identified, the methodology adopted and the transparency with which the reasoning is explained all contribute to the confidence that a Court or Tribunal is ultimately able to place in the expert’s conclusions. By the time an expert enters the witness box, those foundations have already been laid. Cross-examination simply tests whether they are capable of supporting the opinions expressed.
This philosophy is reflected throughout the authorities governing expert evidence. The principles established by Cresswell J in The Ikarian Reefer, subsequently reinforced through CPR Part 35, the Civil Justice Council Guidance for the Instruction of Experts in Civil Claims and the recently published RICS Surveyors Acting as Expert Witnesses (5th Edition), all place far greater emphasis upon the process by which expert evidence is prepared than upon the manner in which it is ultimately delivered. Independence, objectivity, transparency and rigorous investigation are not procedural formalities. They are the foundations upon which confidence in expert evidence depends.
In my own experience, having acted as an Expert Witness, Single Joint Expert, mediator and adjudicator, together with reviewing the work of other experts in professional negligence claims, the reports that cause concern rarely do so because of any lack of technical expertise. More often, the shortcomings relate to the process adopted by the expert. Important documents have not been requested. Alternative explanations have not been investigated. Assumptions have been accepted without sufficient scrutiny. Evidence inconsistent with the expert’s conclusions has received little or no consideration. Occasionally, it appears that the conclusion was reached first and the reasoning assembled afterwards. None of those shortcomings is created during cross-examination. They exist within the report itself and merely become easier to identify when subjected to forensic examination.
One of the greatest misconceptions surrounding expert evidence is that confidence equates to credibility. In my view, that is rarely the case. A confident expert who has failed to investigate the evidence properly is unlikely to become more persuasive when challenged. On the contrary, confidence unsupported by transparent reasoning often makes deficiencies more apparent. Conversely, an expert who openly identifies assumptions, acknowledges limitations within the available evidence and explains logically why particular conclusions have been reached will frequently command greater confidence because their reasoning is capable of independent scrutiny. Credibility is earned through analysis rather than assertion.
There is another perspective which, in my view, deserves greater consideration. Having served as an adjudicator in a significant number of construction disputes, I do not have the benefit of seeing experts cross-examined. Expert evidence is almost invariably presented in the form of written reports, together with any responses to questions or comments made during the adjudication. The report must therefore stand on its own merits. There is rarely any opportunity for an expert to clarify an ambiguous opinion, explain an omission or repair shortcomings in their reasoning through oral evidence. The adjudicator is required to evaluate the report as presented and determine what weight should properly be attached to it.
In those circumstances, the quality of the report assumes even greater significance. The most persuasive reports are rarely those expressed in the strongest or most uncompromising terms. Rather, they are the reports that demonstrate a logical and transparent methodology, engage fairly with the contemporaneous documentation, acknowledge evidence that may detract from the conclusions reached and explain, through careful reasoning, how the expert has progressed from the factual material to the opinion ultimately expressed. Conversely, reports that appear argumentative, selective in their treatment of the evidence or reluctant to acknowledge obvious limitations are often considerably less persuasive, irrespective of the technical expertise or experience of the individual who prepared them.
The same observations apply equally to litigation and arbitration. Cross-examination undoubtedly remains one of the most effective mechanisms for testing expert evidence, but it should not be viewed as the point at which credibility is either created or destroyed. More often, it merely exposes the strengths and weaknesses that already exist within the report. An expert who has undertaken a thorough investigation, challenged their own assumptions, engaged fairly with opposing evidence and explained their reasoning transparently has usually established their credibility long before they take the witness stand. Equally, an expert who has failed to do those things is unlikely to repair those shortcomings through even the most accomplished oral evidence.
Perhaps this also explains why the recently published RICS Surveyors Acting as Expert Witnesses (5th Edition) places such emphasis upon the processes underpinning expert evidence rather than simply the finished product. The guidance recognises that credibility is not achieved by carefully drafted declarations of independence or by reproducing the wording required by CPR Part 35. It is demonstrated through the professional disciplines applied throughout the instruction, from the moment the appointment is accepted until the final report is signed.
Ultimately, I do not believe Expert Witnesses lose credibility in court. In most cases, they lose credibility months earlier through the decisions they make whilst preparing their evidence. The quality of their investigation, the transparency of their reasoning, the robustness of their methodology and their willingness to engage objectively with all of the available evidence determine how persuasive their opinions will ultimately prove to be. Cross-examination simply shines a light upon those matters. It rarely creates the weaknesses; it merely reveals them. In my view, that is one of the most important lessons for every Expert Witness, irrespective of discipline or experience.