There is a general rule that opinion evidence is not admissible because the function of a witness is to give evidence of fact. However, sometimes it is appropriate for opinion evidence to form part of a case.
Under section3 (2) of the Civil Evidence Act, a witness may give a statement of opinion if made as a way of conveying relevant facts personally perceived by them.
Expert witnesses are permitted to give their opinion in Court. The admission of expert evidence is governed by Part 35.
Part 35.4 places limits on the ability of parties to rely on expert evidence. It states:
(1) No party may call an expert or put in evidence an expert’s report without the court’s permission.
(2) When parties apply for permission, they must provide an estimate of the costs of the proposed expert evidence and identify –
(a) the field in which expert evidence is required and the issues which the expert evidence will address; and
(b) where practicable, the name of the proposed expert.
(3) If permission is granted it shall be in relation only to the expert named or the field identified under paragraph (2). The order granting permission may specify the issues which the expert evidence should address.
Experts have an overriding duty to the Court. This is stated in Rule 35.3 which states:
1) It is the duty of experts to help the court on matters within their expertise.
(2) This duty overrides any obligation to the person from whom experts have received instructions or by whom they are paid.
the evidence be given by a Single Joint Expert (SJE). The Court will decide whether an SJE is appropriate depending on a number of relevant factors. It is usual for an SJE to be instructed on the fast track unless there is a good reason not to do so.
On the multi-track, it is more common for parties to instruct their own experts. Where separate experts are instructed, the Court will make directions in order to make the exchange of expert evidence as efficient as possible.
Paragraph 3.1 of Practice Direction 34 gives the form and content for an expert report.
This states as follows:
3.1 An expert’s report should be addressed to the court and not to the party from whom the expert has received instructions.
3.2 An expert’s report must:
(1) give details of the expert’s qualifications;
(2) give details of any literature or other material which has been relied on in making the report;
(3) contain a statement setting out the substance of all facts and instructions which are material to the opinions expressed in the report or upon which those opinions are based;
(4) make clear which of the facts stated in the report are within the expert’s own knowledge;
(5) say who carried out any examination, measurement, test or experiment which the expert has used for the report, give the qualifications of that person, and say whether or not the test or experiment has been carried out under the expert’s supervision;
(6) where there is a range of opinion on the matters dealt with in the report –
(a) summarise the range of opinions; and
(b) give reasons for the expert’s own opinion;
(7) contain a summary of the conclusions reached;
(8) if the expert is not able to give an opinion without qualification, state the qualification; and
(9) contain a statement that the expert –
(a) understands their duty to the court, and has complied with that duty; and
(b) is aware of the requirements of Part 35, this practice direction and the Guidance for the Instruction of Experts in Civil Claims 2014.
The report must be verified by a statement of truth just like with an ordinary witness statement.
You may be interested to read some of the standard directions that Courts make with respect to expert evidence. These can be found here.