https://www.slab.org.uk/guidance/type-of-expert-witnesses-and-their-qualifications/
When choosing an expert, you should consider whether they are appropriate for the particular case.
Before authorising the use of a “distant” expert, you must satisfy us that no comparable witness is available in the vicinity of the court.
You should always ensure, at the outset, that your chosen expert is able and willing, if necessary, to attend court in due course to speak to the report.
An expert is a person whose role is to speak primarily to opinion evidence, rather than to evidence of fact alone, and who has the requisite knowledge, professional skills and qualifications to provide an opinion (and/or undertake relevant associated steps).
Examples of expert witnesses include:
If the individual named in the application does not meet the definition of an expert then we will refuse the application and advise you that prior approval is not required to instruct an individual who is not an expert but is a witness to fact.
Our prior approval is not required to instruct an individual who is a witness to fact.
Examples of factual witnesses are:
You need to supply us with the following information detailing their:
We need to be satisfied that the expert has the appropriate skills and expertise to comment on the matter at hand. Often experts are professionals and where this is the case you would expect them to be engaged in practice, so that they have recent and up to date knowledge and experience in their field of expertise.
Some types of experts are not professionals engaged in private practice, but instead are individuals with relevant qualifications and expertise, such as academics. It is important that you tell us that you are satisfied that they are regarded as experts in their field, and that the court is likely to have regard to their opinion.
If insufficient information is provided then we will continue the application for the required information. If it is unclear as to whether the expert has the required expertise in the field in which they are being asked to provide an opinion we may ask for a copy of the expert’s CV.
Approval for an expert witness
Additional guidance on specific expert witnesses – defence post mortems, drug experts, psychologists, psychiatrists, forensic accountants