When Expert Evidence Goes Wrong – The 5 Common Mistakes – Part 5

Part 5: The Expert Who Is Unprepared For Challenge

The expert report is not the end of the assignment.

An expert may have produced a careful and well-reasoned report but still weaken their evidence if they are not properly prepared for the stages that follow. Experts’ meetings, joint statements and cross examination all require the expert to understand not just the conclusions reached, but the evidence, assumptions and reasoning behind them.

The purpose of preparation is not to teach the expert how to defend every sentence. It is to ensure that the opinion remains clear, independent and capable of being explained under challenge.

Know the report

A report may take many months to prepare and pass through numerous drafts. By the time it is served, the expert may remember the broad conclusions but not every document, assumption or qualification that led to them, which can quickly create problems.

The expert should therefore revisit the final report carefully and understand the basis of each material conclusion. This includes the important source documents, assumptions relied upon, areas of uncertainty and any points where the opinion depends on the court accepting a particular factual position.

It is particularly important to work from the final report rather than an earlier draft. Changes made during drafting may have altered the wording, qualification or scope of an opinion.

The experts’ meeting

An experts’ meeting is not simply another stage of adversarial litigation. Its purpose is to identify where the experts agree, where they disagree and why. That requires each expert to engage genuinely with the other expert’s reasoning.

An expert who enters the meeting determined to preserve every conclusion in the report is unlikely to assist that process.

The meeting may reveal that an apparent disagreement results from different assumptions, terminology or data rather than a genuine difference of expert opinion. Equally, the other expert may identify a point that causes an opinion to change. That should not be regarded as a failure.

A useful experts’ meeting narrows the issues and helps the court understand the true areas of disagreement.

The joint statement

The joint statement can be one of the most important expert documents in the case. It should clearly record the matters agreed, the matters still disputed and the reasons for each disagreement. It should reflect the experts’ own opinions rather than become another vehicle for the parties’ submissions.

Where an expert has changed or qualified an opinion, the joint statement should say so clearly. Trying to preserve an earlier position through ambiguous wording is likely to create greater difficulty later.

The strength of the joint statement lies in its clarity.

Preparing for cross examination

Cross examination tests more than technical knowledge. The expert may be challenged on the evidence relied upon, assumptions made, conclusions reached and any apparent inconsistencies between the report, joint statement and oral evidence. Preparation should therefore focus on understanding the opinion rather than rehearsing answers.

The expert should know which conclusions are most open to challenge and should have considered the strongest arguments against them. They should also be familiar with important contrary documents and be able to explain why those documents do or do not affect the opinion.

An expert who has never seriously considered the opposing case may encounter it for the first time in the witness box, which is not the place to begin testing the analysis.

Concessions are not a failure

One of the most damaging behaviours in cross examination is an unwillingness to concede an obvious point. The expert may believe that every concession weakens the client’s case. In practice, refusing to accept a fair proposition can damage credibility far more than the concession itself. In fact, a reasonable concession demonstrates independence.

The same applies where the expert does not know the answer. If a question cannot properly be answered without reviewing a document or calculation, the expert should say so. Guessing is rarely helpful. Likewise, if a question falls outside the expert’s expertise, that should be made clear to the Court.

The expert’s role is not to have an answer to everything.

Answer the question

A common weakness in oral evidence is answering more than has been asked.

Experts sometimes give lengthy explanations when a short answer would have been sufficient. They may anticipate where counsel is going or try to qualify every response before the question has fully developed. This can make clear evidence appear defensive.

The better approach is usually to listen carefully; answer the question asked and explain further only where necessary. An expert should definitely not engage in an argument with counsel. Nor should they treat cross examination as a contest to be won.

The purpose is to assist the court.

Changes of opinion

An expert’s opinion may change after the report has been served. This can be for many legitimate reasons; further documents may emerge; an assumption may prove incorrect; or the other expert may identify an issue that requires reconsideration.

The important point is not that the opinion changed, but why it has changed.

A change based on proper analysis demonstrates independence. Attempting to conceal or minimise that change because it is inconvenient to the client can have the opposite effect. The expert should be able to explain clearly what changed, why it changed and what effect it has on the remaining conclusions.

The value of preparation

Good preparation does not make an expert immune from difficult questions and it should not be intended to. It allows the expert to understand where the opinion is strong, where it is qualified and where reasonable disagreement exists. They should enter the witness box prepared to defend conclusions that remain justified and equally prepared to concede points that do not.

An expert who approaches challenge in that way is far more likely to retain the court’s confidence.

The strongest expert is not the one who can defend every answer, but the one who knows which answers can be properly defended.