Maintaining Effective and Professional Relationships with Experts
Experts are important witnesses in any trial or hearing that involves complex matters which are beyond the ordinary knowledge or understanding of the judge or jury. However, an expert must be independent, unbiased and give evidence that is based on their expertise.
They do not necessarily need to have qualifications. For example, a police officer who has extensive experience of watching and analysing CCTV footage may be permitted to give expert evidence about particular CCTV footage.Although an expert is not an advocate, their role, like an advocate, is to assist the court. An expert should not stray beyond their field of specialism when giving evidence or this could amount to opinion evidence that does not fall within the exceptions to the hearsay rules (see Chapter 5). An expert's report must be disclosed to the other party if it is to be relied upon at trial (see CPR Part 35.13 and CrimPR Part 19.3).
Ward (2020) argues that the lack of a clear test as to the reliability of expert evidence is problematic and argues that the courts should move to formalise a more stringent
test in line with the safety test in hearsay evidence (we will discuss hearsay evidence in Part B). The common law has essentially developed a loose test that the expert's evidence must have a sufficiently reliable scientific basis before it can be admitted into evidence (see for example the Australian case of R v Bonython (1984) 38 SASR 45 that has been cited by the English courts).
4.6.1 The Expert's Duty
Regardless of which party instructs and pays the fees of an expert, the expert's duty is to the court. This means that their report is prepared for, and addressed to, the court and they can apply to the court for any orders or directions if they feel they are being unduly pressured by the party instructing them.
The bi-partisan nature of an expert is clearly set out in civil proceedings under CPR Part 35 and in criminal proceedings under CrimPR Part 19.In civil proceedings an expert has an overriding duty to help the court on all matters within its expertise (see CPR Part 35.3). Similarly in criminal proceedings CrimPR Part 19.2 imposes an overriding duty on an expert to, in addition, give objective and unbiased opinion and assist the court in fulfilling its case management functions. Like advocates, experts are also expected to help the court achieve the overriding objective.
4.6.2 The Expert's Written Report
The court decides whether expert evidence can be used. For example, in civil proceedings this power is found in CPR Part 35.4 and Civil Evidence Act 1972, s. 2. The use of an expert will usually be restricted to one expert per party from a particular field (e.g. one medical expert, one forensic accountant expert, etc). In civil proceedings it is not necessary to call an expert to testify if the parties agree to rely on written evidence. In criminal proceedings an expert is usually required to be called to testify (see CrimPR part 19.3(4)(b)) unless the parties agree or the court directs the expert need not attend.
The format of an expert's report is also prescribed by the procedural rules. CPR Part 35.10 and PD 35 paras 3.1-3.3 set out what an expert's report should contain in civil proceedings. In criminal proceedings this is to be found in CrimPR Part 19.4. An advocate should ensure that when perusing expert reports the report is in the correct format and contains the information required by the relevant court under the relevant procedural rule. Generally, reports should include details of an expert's qualifications, details of the literature the expert has used, summarise a range of differing opinions of the topic under examination and summarise the expert's own opinion with reasons for those opinions.
In criminal proceedings an expert is expected to serve with their report anything which the party serving the report is aware might (1) be thought capable of undermining the reliability of the expert's opinion or (2) detracting from the credibility or impartiality of the expert and (3) an explanation of how facts stated in the report
are admissible as evidence (see CrimPR Part 19.3(3)(c)).
In addition, if a witness of fact gives evidence where any part of it may be regarded as expert evidence then that evidence may have to comply with the requirements for an expert under CrimPR Part 19 although the court can make adaptions to those rules (see CrimPR Part 19.1(3)).An expert must also give certain declarations about the validity of their report. For civil proceedings an expert's report must contain a statement of truth (see CPR PD 35 para 3.3). In criminal proceedings the expert's report must contain a ‘declaration of truth' (see CrimPR Part 19.4(k) and CrimPR Part 16.2(b)).
Expert’s Declaration of Truth in Criminal Proceedings
I declare that this report is true to the best of my knowledge and belief and that I am aware that if it is introduced in evidence, then it would be an offence wilfully to have stated in it anything that I know to be false or do not believe to be true.
Expert’s Statement of Truth in Civil Proceedings
I confirm that I have made clear which facts and matters referred to in this report are within my own knowledge and which are not. Those that are within my own knowledge I confirm to be true. The opinions I have expressed represent my true and complete professional opinions on the matters to which they refer. I understand that proceedings for contempt of court may be brought against anyone who makes, or causes to be made, a false statement in a document verified by a statement of truth without an honest belief in its truth.
Under CPR 35.6 a party may put written questions to an opponent's expert about their report and where possible experts are expected to narrow the issues that are in dispute to save court time. The court also has the power to decide that only one single expert is used in the case (see CPR 35.7 and CrimPR Part 19.7) rather than an expert for each party. An advocate should ensure that the expert understands their duties and responsibilities under the relevant civil procedure rules.