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What makes a good expert witness in environmental disputes?
  • Sep 14, 2021
  • Latest Journal

Sarah Lovell, expert witness lead at Ricardo (the global environmental, engineering and strategic consultancy), is a specialist in waste permitting and regulatory compliance. Sarah has acted as an expert witness since 2019 and applies her experience as a consultant, and previously a regulator for the Environment Agency, to a range of commercial disputes and criminal proceedings. In addition to providing pre-action advice, she has authored numerous court compliant reports and has given evidence in court under cross examination twice.

Sarah coordinates a team of senior consultants who provide expert opinion and witness services in a wide range of commercial and contractual disputes, insurance claims, criminal cases, and public and planning enquiries. In this article, Sarah shares her experience of what makes a good expert witness and the pitfalls to avoid.

Clearly, having suitably qualified and experienced consultants with specialist expertise relevant to the specific issues of the case is one crucial success factor in providing expert witness services. Recent cases that our experts have been involved in range from alleged breaches of environmental permits and the waste duty of care code of practice, to disputes relating to the construction and performance of energy from waste infrastructure, so there must be other, more common, factors involved.

Most importantly, an expert should understand and be up to date with the criminal and civil procedure rules, which should ensure that all expert reports are consistent with current court rules, practice and protocols. Fundamental to these rules, is that expert witnesses must understand that their role is to be unbiased and accurate, and that their obligation is to the court. It is not the role of an expert to advocate for their client and any expert found to be doing so will ultimately do their client a disservice. This has been highlighted in a number of recent cases where the expert’s impartiality has been criticised by the judge.

It’s not uncommon for experts to come under pressure from their clients to provide more supportive opinions. In Ricardo’s experience, this is especially true where clients feel they are being subject to harsh treatment by the opposition. This sometimes can occur because many of the regulations affecting waste activities are used as policy tools and are designed to drive particular behaviours.

For example, Landfill Tax is charged on materials disposed of at a landfill site as an incentive to minimise the amount of material produced and the use of non-landfill waste management options.Since 1 April 2018, this tax has been extended in England and Northern Ireland to apply to material disposed of at an unauthorised site,as set out in ‘Excise Notice LFT1: a general guide to Landfill Tax’(published by Her Majesty’s Revenue and Customs (HMRC) and updated 9 April 2020). When waste – including waste thatis readily recyclable such as wood – is illegally disposed of (deposited without a permit),landfill tax is applied to that waste at the standard rate.No credits are available and a penalty of up to 100% may also be charged depending on HMRC’s view of the level of assistance provided to them by the operator of the unauthorised site. At unauthorised sites,the tax is also chargeable by weight and the weight of material will be determined by reference to the volume of the disposal. Once the volume of material has been estimated, it will be multiplied by the conversion factor 1.5 to determine the weight (regardless of waste type).

To the uninitiated defendant, this can seem punitive, especially for waste types thatwould, under normal market conditions, be recycled and so would not typically be subject to Landfill Tax at all. The key issue being whether the waste has been disposed of at an unauthorised site. If it has, there is no reasonable argument thatLandfill Tax doesnot apply at the standard rate.

In cases such as this, it is important that an expert has the ability to make complex technical issues understandable and provide clear explanations for the basis of their opinion that are reasonable, and evidence based. This can be as valuable to their client as it is to the court, as it can usefully inform any decisions regarding which battles to pick.

No client would welcome a judge’s criticism of their expert’s credibility. Therefore, a well-reasoned report that has undergonea process of internal quality assurance to effectively ‘stress test’ its conclusions will help guard against this.

A good expert witness will be cognisant of their own limitations and will only make statements that they can justify. They should be able to recognise questions to which the answer would be outside their area or areas of expertise and respond accordingly – including admitting where they don’t have the expertise to provide an opinion. However, this should not be perceived as a weakness. The more resilient the opinion an expert gives, the harder it is for the opposing counsel to challenge and more likely it is that the judge will be able to agree with an expert’s report in full. For me, as an expert witness, there is no higher accolade I can receive.

Experts must also be careful to avoid any conflicts of interest (perceived or otherwise) and openly disclose any possible conflicts prior to their involvement. In cases where there is a clear conflict of interest –for example,there is a personal relationship between the expert and the instructing party (or the opposition) –it would be inappropriate to accept such an instruction. There are also other, less clear situations that could amount to a conflict of interest and so should be disclosed to the instructing party along with any proposed mitigation at the earliest opportunity. For example, where another expert employed by the same consultancy is acting in another capacity related to the same case.

In summary, an expert witness’s duty is to the court. Therefore, their value to your case lies in establishing and maintaining utmost credibility with the judge. In turn, this relies onthe ability of your expert to demonstrate their independence and the robustness of their opinion, just as much as their subject matter expertise.

Ricardo’s expert capability is founded in the extensive experience and diverse backgrounds of our senior specialists in waste, energy, water and air quality, which is founded on our direct experience in regulation, industry and policy. Crucially, we understand that while the opposition counsel is likely to want to try to discredit your expert, choosing a consultant who demonstrates the highest levels of integrity and avoids bold, if apparently helpful, claims unless they can be reasonably substantiated, is the surest way to avoid this being able to undermine your case.

To find out more about Ricardo’s expert witness services covering waste and resource management, energy, water and air quality, please visit or email