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FREE BOOK CHAPTER: Single Joint Experts (From 'On Experts: CPR35 for Lawyers and Experts' by David Boyle)

16/11/16. CPR35.7 allows the court to direct that if two or more parties wish to submit expert evidence on a particular issue, that evidence should be given by a single joint expert. The court can decide who that expert should be, or how the identity of that expert should be decided, if the parties cannot agree on who should prepare that report.

The Practice Direction to CPR35 sets out the factors to which the court should have regard in making decisions about expert evidence and whether to order a single joint expert.

The first issue to which the court will have regard is whether it is proportionate for each party to have separate experts on that specific issue, having regard to the amount in dispute, the importance to the parties and the complexity of the issue. That is simply a reflection of the Overriding Objective, but it is worth noting that it pertains to the particular issue to be considered by that expert. Whilst it might be proportionate for both sides to have their own expert on, say, the prognosis for a damaged joint, is it really going to be necessary to have two separate experts opining on the prognosis for the scarring which results from the surgery?

Moreover, the wording ‘separate experts for each party’ allows the court to consider whether, in a given case, some parties might jointly instruct an expert whilst others should be outside that instruction. The classic case is where a claimant claims damages for a disease (e.g. Noise Induced Hearing Loss) where there are multiple defendants. There might be an argument as to noise levels, or the apportionment between the defendants, where a single, jointly instructed, engineer might be imposed upon all the parties, but the court might also order that the various defendants jointly instruct an ENT surgeon to counter the claimant’s medical expert.

The second issue is whether the use of a single joint expert will assist the parties and the court to resolve the issue more speedily and in a more cost-effective way than separately instructed experts. This is a potentially difficult area, because there will be cases (e.g. head injury cases) where repeat neuro-psychological testing within a short space of time will skew the results on the second examination, rendering it unreliable. To give parity of arms to the defendant (as it is normally the claimant whose expert examines first) causes an inevitable delay. The alternative, however, is to impose a single joint expert in a case where the brain injury might be of significant value and the claimant’s solicitors, understandably, want to have control over the evidence in that regard. Moreover, where the expert is likely to be central to the determination of the case, a party would understandably want to be able to confer with the expert and test that evidence before going to court. The court has the power to impose a single joint expert, but much will depend on the views of the parties. If both parties are resolutely against the idea and can give good reasons for that, the court should be slow to interfere, but a different judge on a different day might take a different view. Other factors are likely to become relevant in such circumstances.

The third issue to which the court should have regard given 35PD7 is whether the evidence is being given on the issue of liability, causation or quantum. In each case, the court will have to have one eye on whether the issue is likely to be dispositive, and the court will be careful not to box itself in - it is not the expert’s job to decide a case. If the court is of the view that a single joint expert is appropriate on that issue, the parties will need to encourage the court to define the extent of the expert’s report with care, advising the court of all relevant issues (and the expert’s take on them) but ensuring that the court still has free reign over the decision-making process.

There are numerous scenarios where the court might consider that a single joint expert on liability is appropriate. One seen on a regular basis is the case where an employee who suffers injury at work when his workplace is targeted by a robber seeks to introduce evidence as to the reasonableness of the security measures in place. The court might feel that some sort of expert evidence is appropriate in those circumstances, as to industry standards, the potential cost and the potential benefits and difficulties which any given step might have. The difficulty comes in knowing where to draw the line. Is the expert the right person to comment on the methodology of a risk assessment? What data should be considered? Is a change in industry standard actually for the better, or just a trend? The defendant might have its own view on such points and may have its own lay evidence which the court will have to consider, and the difficulty is as to whether the expertise of the lay witness renders his opinion evidence admissible. He may, of course, have more expertise on the specific point than the expert.

It is imperative in those circumstances that the issues on which the expert is instructed to opine are closely defined. Moreover, even if the expert is a single joint expert, that does not mean that he is immune from cross-examination or the rejection of his evidence. He must be careful not to place himself in the position of advocate for one side or the other. The problem arises because the judge making the case management order for expert evidence may never have seen such a case before. The onus in those cases is surely on the parties to explain at the CCMC the precise issues upon which the evidence is sought and the reasons why a single joint expert is, or is not, appropriate.

A scenario where evidence is normally given by a single joint expert is engineering evidence in Noise Induced Hearing Loss claims. There, the question is whether, from the lay evidence, the noise levels were likely to be injurious, and, following on from that, whether the exposure (and therefore the injury) can be proportioned between different defendants. Those reports go to both liability and factual causation, if not medical causation, which is another matter.

In cases where the evidence in question goes to medical causation, single joint experts are relatively rare, because medical causation is often the single most determinative issue in the case, so the parties tend to want to maintain control over the evidence. The court may take a different view, but should have in mind the questions: “What is the point of getting this evidence? What might be the range of opinion? How sure can one be that the expert in question is going to assist in that regard?” Those questions should arise in every case, but are often left unasked or, worse, unanswered. One case where such a course is potentially useful is where there is one preeminent expert in the field, and the parties would both want to utilise his services. There are occasional medical conditions which are so specialised that there are acknowledged experts, to whom other more generalist experts defer. Both sides might, for instance, have an orthopaedic surgeon who can opine on the claimant’s general condition, but a single jointly instructed expert might be the best person to opine as to the benefit of specific surgery.

In cases where the question goes to quantum, there is often real scope for the use of a Single Joint Expert, particularly when the issue is a relatively straight-forward one of valuation. Again, the court should make it clear as to what is required of the expert when giving that permission.

This ties in with the fourth issue to which the court must have regard under the Practice Direction – the extent to which the expert evidence falls within a substantially established area of knowledge which is unlikely to be in dispute or whether there is likely to be a range of opinion.

The fifth issue is whether a party has already instructed an expert on the issue in question and whether or not that was in compliance with a practice direction or protocol. If a party has taken pre-action advice on the viability of the claim (which advice might be privileged, which is the eighth point raised) and then seeks to utilise the services of that expert within the claim, only for the other side to disagree with his evidence, either on principle or by reference to its contents, the court may balk at letting the party rely on that evidence as if it were, and had been obtained as, expert evidence. The court might, in those circumstances, allow the party the benefit of expert evidence on that topic, but not from the expert previously instructed, and impose a single joint expert on the parties, again with a specific remit.

The sixth issue to be considered is whether CPR35 questions might alleviate the need for a second expert, whilst the possibility of the single joint expert giving evidence at trial is the seventh.

The danger, in all such cases, is that a party which is dissatisfied with the opinion of the single joint expert will instruct a shadow expert. Such concerns were highlighted at the time of the Woolf reforms, because lawyers were unsure as to how a single joint expert could maintain neutrality, but have been relatively rare in practice. The questions of cost, and cost-efficiency, mean that only in the rarest of cases will parties go to the expense of getting their own expert to undermine a single joint expert, but in those cases the evidence of the single joint expert often starts to unravel as a result of carefully phrased Part 35 questions, or the party who is dissatisfied with his evidence will apply to the court to rely upon their own new evidence.

The Instruction

CPR35.8 sets out the way in which a single joint expert should be instructed. Any relevant party may give instructions to the expert1 , but must, at the same time, send a copy of those instructions to all other relevant parties2 . The court may give directions about the payment of the expert’s fees and expenses3 (in the first instance, as they potentially follow the event in the long run), and any inspection, examination or experiments which the expert wishes to carry out4 . The court can limit the fees to be paid to the expert5 and may even direct that some or all of the relevant parties pay that amount into court6 , but the default provision is that the relevant parties are jointly and severally liable for the payment of the expert’s fees and expenses7 .

The purpose of CPR35.8 is to ensure transparency in the parties’ dealings with the expert. It is that very transparency which makes parties, particularly claimants, cagey about the use of single joint experts in the first place.

It follows that when a single joint expert is to be instructed, particular care needs to be exercised in the content of the instructions, and if a party feels that particular issues need to be considered, they should set them out openly on the face of the letter of instruction and include any relevant documentation for the benefit of the expert. If the point is a good one, there should be no need to lead the expert to that conclusion – the matter should speak for itself, and, once raised, the expert will struggle to ignore it. If the expert does not accept the contention, then the party may need to ask CPR35 questions, or even cross-examine the expert as to why he has rejected what is, in the party’s eyes, a good argument, but an attempt to force a single joint expert to reach a pre-defined conclusion is a dangerous game to try to play.

David Boyle
Deans Court Chambers

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1 CPR35.8(1)

2 CPR35.8(2)

3 CPR35.8(3)(a)

4 CPR35.8(3)(b)

5 CPR35.8(4)(a)

6 CPR35.8(4)(b)

7 CPR35.8(5)

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