The Fundamental Importance of Legal Tests in Expert Evidence

By Giles Eyre, Barrister, 9 Gough Square

When presented with an expert report, a lawyer will often turn straight to the opinion section. The purpose is to identify what the opinions of the expert are before working through the entirety of the report, giving the lawyer the opportunity to see how and to what extent the facts presented in the report lead to the conclusions that the expert ultimately expresses. One consequence of this particular legal habit is that the expert’s ability (or inability) to express his/her concluded opinions using the appropriate legal test, becomes immediately apparent.

A legal test may derive from a statutory provision (from primary legislation or secondary regulation), a term of a contract or a common law rule. Examples of legal tests include the standard of proof (the applicable standard against which any alleged breaches of duty are to be measured) and remoteness, causation and the consequences of damage. The legal test to be applied is ultimately an issue for the lawyers, even though in many cases the expert will be well aware of which test needs to be applied.

If the expert is unsure what test to apply, the first step is always to contact the instructing lawyer and ask. Unfortunately most experts, no matter what level of experience as expert witnesses they may claim, seem not to understand the critical importance of applying accurately (and therefore expressly applying) the appropriate legal test to each opinion expressed in the report. The wording of the test should also be expressed precisely – it should never be paraphrased or glossed.

Once the legal test has been identified, it is the application of the test to the factual basis of the case that often becomes the real challenge. Whether the case requires a forensic accountant to assess the application of an accounting standard to a company’s accounts, a doctor to assess the duty of care owed to a patient during treatment, or an engineer to assess why a structure failed, it is the responsibility of the expert first to accurately express the test in the evidence and then to explain how the court needs to approach the test in the light of the facts of the case.

Most experts do not appreciate the importance of this two-stage analysis of the evidence that correctly expressing the legal test requires. For example, the ‘Bolam test’ (the basic test used for assessing breach of duty in a professional negligence case) is not a test of what the reporting expert ‘would have done’ or indeed what the defendant ‘should have done’ but rather is a test that requires the expert to give opinion as to what ‘no reasonably competent professional’ would have done. Therefore, the Bolam test is a test of exclusion. Unfortunately, many experts do not produce precise evidence in straightforward cases and fall profoundly short of expressing a proper opinion when dealing with more complex factual situations.

It is fundamental to the expert’s role to know how to apply legal tests to the evidence and to express these tests properly. If an expert is unsure what a legal test is or how to use it, it is essential to remedy this lack of forensic skill before writing his/her next expert report.

Giles Eyre

9 Gough Square

23 March 2012

Giles Eyre will give a presentation on Legal Tests in the Professional Solutions Advanced Report Writing Workshop on 19 June 2012: