Giving evidence as an expert witness

10. The role of an expert witness is to help the court on specialist or technical matters that are within the witness’s expertise. An expert witness is able to consider all the evidence available, including statements and reports from the other parties to the proceedings, before forming and providing an opinion to the court.

11. You must make sure you understand exactly what questions you are being asked to answer. If your instructions are unclear, you should ask those instructing you to explain. If the instructions are still not clear, you should not provide expert advice or opinion.

12. You must only give expert testimony and opinions about issues that are within your professional competence or about which you have relevant knowledge including, for example, knowledge of the standards and nature of practice at the time of the incident or events that are the subject of the proceedings.5 If a particular question or issue falls outside your area of expertise, you should either refuse to answer or answer to the best of your ability but make it clear that you consider the matter to be outside your competence.6

13. You must give an objective, unbiased opinion and be able to state the facts or assumptions on which it is based. If there is a range of opinion on an issue, you should summarise the range of opinion and explain how you arrived at your own view. If you do not have enough information on which to reach a conclusion on a particular point, or if your opinion is qualified (for example, as a result of conflicting evidence), you must make this clear.7

14. If you are asked to give an opinion about a person without the opportunity to consult with or examine them, you should explain any limits this may place on your opinion. You should be able to justify the decision to provide your opinion.

15. If, at any stage, you change your view on any relevant matter, you have a duty to make sure those instructing you, the other party and the judge are made aware of this without delay. You should tell your instructing solicitor, who should tell the other people who need to know. If the solicitor fails to do this, you should tell the court about your change of view. If you are not sure about what to do, you should ask the court or get legal advice.

16. You must respect the skills and contributions of other professionals giving expert evidence, and not allow their behaviour to affect your professional opinion.