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Early engagement between the parties on the scope of expert evidence and the methodology to be used is crucial

Following the hearing of an interim application in the case of UPL Europe Limited v Agchemaccess Chemicals Limited, Chief Master Marsh has given some guidance on the obligations of litigants where expert evidence is permitted. This guidance will be particularly useful where expert technical or scientific analysis is required, but it is also of more general relevance in any case where expert evidence is adduced.

One of the key issues in UPL was whether a particular chemical product was “identical” to another product for the purposes of an EU regulation concerning the sale of plant protection products across member states. There was some dispute between the parties as to what made a product “identical” for these purposes. An order was made at the costs and case management conference (CCMC) permitting the parties to adduce expert evidence in the field of chemical analysis, so as to address the question of whether two products were chemically identical.

The claimants’ solicitors subsequently indicated in correspondence that they believed expert evidence was no longer required. Initially, the defendants did not provide a proper response to this correspondence, but later indicated that they were well advanced with the preparation of their expert evidence and refused to engage in a discussion about the appropriate methodology.

In the circumstances, the claimants’ solicitors followed through on a threat to make an application seeking an order that permission to rely on expert evidence in the field of chemical analysis be revoked. In the alternative, they sought an order that the defendants should clarify the proposed scope of their expert evidence and that there should be sequential exchange of the evidence.

After considering the application, Chief Master Marsh found that no adequate reason had been given by the defendants for their lack of engagement. Although the defendants had tried to characterise the approach of the claimants as aggressive, he concluded that in fact the approach of the claimants had been “measured”.

Chief Master Marsh went on to say that it will almost always be necessary for there to be a discussion in advance about the scope of expert evidence in cases where it is permitted. This is particularly true of cases involving detailed scientific analysis, where the parties should attempt to agree on the subject of the analysis and the appropriate methodology in advance. He suggested that the only exception to this should be in cases where the scientific approach to be adopted is “well established and unlikely to be contentious”; otherwise, there was a risk that the reports may not be properly comparable.

Chief Master Marsh was not prescriptive about how these discussions regarding scope and methodology should take place, nor about whether they should be between solicitors or experts. This was something that should be determined on a case-by-case basis, and it will usually depend on the particular subject matter and the nature of the experts’ fields of expertise.

It was made clear in the judgment that, in every case where the parties have permission to rely on expert evidence, the parties must cooperate with one another to ensure that the evidence is properly focused on the issues, and that the reports of opposing experts are properly “matched”. Chief Master Marsh anticipated that, if this was done in every case, the result should be that expert evidence is shorter and more tightly focused on the core issues. He went on to suggest that the court should consider giving a direction for a discussion about the scope of expert evidence and the appropriate methodology well in advance of the date for exchange of expert reports.

At the hearing, the claimants did not pursue an order that permission to rely on expert evidence should be revoked. In the end, the court ordered that the claimants and defendants should discuss the scope and methodology of the expert evidence, and try to agree a joint statement on the subject. Nevertheless, the court granted the claimant 85% of its costs of the application.


As Chief Master Marsh himself acknowledged, the decision in UPL does not recommend a new approach. However, it does emphasise the importance of timely cooperation between the parties. It also highlights the particular problems which can arise when parties’ expert evidence is produced without proper engagement over questions of scope and methodology. Furthermore, it makes clear that parties who do not engage in discussions about questions of scope and methodology when invited to do so can be penalised in costs.

In cases where experts are to carry out detailed technical analyses, there are often conflicts of approach which, if not resolved in advance, would result in the evidence of the experts not being directly comparable. This can result in more costs being incurred and effectively wasted in the long term. In light of Chief Master Marsh’s guidance, parties will need to consider how and when to approach questions of scope and methodology. It is advisable for these issues to be addressed at the earliest opportunity.

At the point at which a party is considering whether to ask the court’s permission to rely on expert evidence, the scope of that evidence (and the methodology to be used, if applicable) should be carefully considered. If the parties are filing agreed directions in advance of a CCMC, which include a direction for expert evidence, they would ideally have discussed scoping issues at the point when the draft directions were being negotiated, so that the terms of the order granting permission for expert evidence can be tightly focused. Otherwise, the parties should consider including in their draft directions a requirement for either the parties’ legal representatives or the experts themselves to discuss issues of scope or methodology, and attempt to reach agreement well in advance of the date for exchange of expert reports.

In some technical cases, there will be multiple possible methodologies which the experts could adopt. It may well be appropriate for the experts to meet and attempt to reach agreement in these circumstances. If the parties are unable to agree on the methodology to be used in advance, there may be a direction compelling the parties to take a particular step (such as informing the court of the points of disagreement).

Where agreement on methodology cannot be reached, it will usually be appropriate for the experts to report on the merits of their own chosen methodology by comparison with the methodology selected by their counterpart, in addition to reporting on their substantive findings. This should assist the court when assessing the appropriateness of the alternative methodologies used, and, ultimately, the weight to be given to each expert’s evidence.

The guidance in practice: a worked example

If two experts in the field of acoustics were separately instructed to report on noise penetration within a six storey, multi-let building, it is conceivable that one expert could approach the issue by measuring the noise levels in the subject property, whilst the other expert could decide instead to analyse the sufficiency of the soundproofing within the building. Both approaches may be legitimate, but unless the methodology to be used is agreed in advance, the experts’ reports are likely to be of limited use to the court.

In this example, the trial judge would need to take into account the methodology used when determining the weight to be given to each expert’s evidence. It would be very difficult for the judge to carry out a direct comparison of the evidence when the methodology used in each case is so different.

The parties’ legal representatives could hold discussions on the scope of the expert evidence to determine which parts of the subject building should be assessed for noise penetration. If, for example, the dispute is focussed on noise penetration between a ground floor retail unit and first floor office premises between 9am and 5pm, the parties may agree that the experts should assess the level of noise only on the first floor and only during working hours. In such a case, it may not be helpful for the experts to carry out a broader assessment of noise penetration within the whole building, including the upper floors.

It would also be advisable for the noise penetration experts to discuss between them which methodology would be the most appropriate in the circumstances in the hope that agreement could be reached.

It would be helpful for the parties’ legal advisers to agree draft directions which carefully define the scope of the expert evidence as limited to the relevant floors and the relevant times of day. Since methodology is a contentious issue in this example, the draft directions should also make provision for the experts to discuss and attempt to agree the appropriate methodology in advance of reports being prepared. If agreement cannot be reached on scope or methodology, it may be helpful for there to be a direction requiring points of dispute on scope and methodology to be filed, and, potentially, a requirement for the parties to seek further directions from the court in these circumstances.

Boodle Hatfield Rachel Standing

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