Independent expert witnesses

  • Published: January 23, 2019
  • Author: Paul Sankey, Partner, Enable Law

What does independence mean?

Expert witnesses are required to be independent and impartial. The Civil Procedure Rules (CPR) say, "Expert evidence should be the independent product of the expert uninfluenced by the pressures of litigation" and "Experts should assist the court by providing objective, unbiased opinions on matters within their expertise, and should not assume the role of an advocate" (CPR Practice Direction 35.2.1).

Expert witnesses falling short: judicial criticism

In a number of reported decisions, experts have been criticised for a lack of objectivity. Here are two examples of adverse comments by judges about experts:

Of Prof M: "I regret to say that in the course of listening to Prof M, I formed the impression that he has also developed what might be regarded as experts in giving evidence. Prof M was extremely careful in giving his answers. I increasingly took the view that this was because his first priority was to avoid saying anything that might damage [the defendant's] case[1]."

Of Dr J: "There was a lack of balance and much argument in his evidence. Rather than answer a question directly, Dr J would often sidestep and respond with an argument to support the claimant's position[2]." 

The 'useful test of independence'

The Civil Justice Council's Protocol for the Instruction of experts offers one 'useful test of independence'. The test is whether the expert would express the same opinion if instructed for the other party. This is a test widely adopted by experts.

When surveyed for a recent report for the Expert Witness Institute[3], most experts were confident of their independence but less confident about that of other experts. A total of 92% of experts agreed that their opinions would be the same if instructed by the other party, although half agreed that they have to consciously resist adopting the role of an advocate. (In other words, they heroically overcome temptation.) Half disagreed with the statement, "Expert witnesses I come across in my field never assume the role of an advocate". Double negatives aside, this suggests that half of the experts think other experts act at times as advocates.

A more comprehensive test of independence

The researchers concluded that the 'useful test' is not enough. Whilst the test focuses on experts being tempted to take sides, there is more to independence than this. The independence of experts can be compromised by:

  • personal or professional bias towards a particular theory
  • allegiance to an individual or organisation other than a party
  • an indirect financial interest in the outcome of the case
  • an unconscious 'litigation bias'.

A checklist for expert witnesses (The Expert Witness Institute)

The report suggests a checklist for experts to take them beyond the 'useful test'. Has the expert witness…


  1. …agreed in explicit terms with those instructing them that they comply with The Ikarian Reefer principles and relevant rules and practice directions? In a shipping case known as The Ikarian Reefer [1993], 2 Lloyds Rep. 68, Mr Justice Cresswell laid out what has widely become accepted as the classic statement of the duties and responsibilities of expert witnesses. These principles are largely now reflected in the Civil Procedure Rules, but see my blog 7 Classic Principles for Expert Witnesses for comments on their continued applicability.

Conflicts of interest

  1. …checked for conflicts of interest using an appropriate system?
  2. …complied with their duty to disclose any actual or potential conflicts?

Instructions and feedback

  1. …agreed timing and content of material to be supplied with their instructions?
  2. …agreed expectations for feedback on their draft report?
  3. …agreed expectations for feedback on the use to which their report was put?
  4. …communicated to those instructing them concerns, if any, about the opposing expert's duty of independence and impartiality?


  1. …disclosed their method of analysis?
  2. …disclosed, where it exists, the industry standard/s and whether they have complied with it/them?
  3. …disclosed at the earliest opportunity all matters which affect the actual or apparent independence or impartiality of their opinion?

***You might also be interested to read Paul Sankey's blog, '7 classic principles for expert witnesses'.***

[1] Edward Lifesciences v Boston Scientific, [2018] EWCA Civ 673 
[2] Ruffell v Lovatt 2018 
[3] Towards Expert Witness Independence and Impartiality: A Research Report for the Expert Witness Institute by Professor Penny Cooper and Dr Michelle Mattison, 14 November 2018

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