Change your expert, risk your case!

Instructing expert witnesses in high value, technical disputes is an inevitability. Often multiple experts per party are required. Unless there is factual evidence that is central to the claim, expert evidence is a fundamental factor in determining who wins and who loses at trial. 

Experts’ duties and obligations are always owed to the Court, not to the parties who instructed them. It is common and, indeed, desirable, for an expert to concede some points and accept elements of another expert’s reasoning over their own when challenged. Especially during oral cross examination at trial. This demonstrates to the Judge that the expert is aware of and is fully complying with their duties of impartiality. 

Expert instruction and involvement can be riskier in longer running claims, especially if there is a change of expert. The recent case of Skykomish Ltd v Gerald Eve LLP [2025] EWHC 1031 (Ch) is a case in point. 

Summary of the case

Skykomish Ltd (S), a property development company, brought a claim in negligence against a valuer Gerald Eve (GE) for alleged negligent valuation of a Purpose Built Student Accommodation (PBSA) development in 2015. The claim was started before 2019 so had been running for at least six years before trial began in March 2025. Again, because of the complexity and amount of work involved, it is not uncommon in high value complex disputes to have a few years pass between starting the claim and the trial. In this case, during that period, S had instructed two previous experts, before appointing the expert who ultimately appeared at trial. All three experts were from the same property services company (a well-known international organisation). A key reason for the change was that S’s team considered that the dispute had become much more focused on PBSA, something S’s previous experts were less experienced in. 

At trial, S’s expert gave evidence on a number of points. When challenged, it transpired that she had made some errors in her calculations, including some significant ones regarding the valuation of the development at the centre of the dispute. 

The problem here wasn’t S’s expert witness’ expertise nor her integrity (she readily accepted that the mistakes had been made). The Judge gave credit for that but he noted “…candid admission upon discovery is not the way the system is supposed to work.” The Judge believed that had S’s expert had more time following her appointment, she would have presented a more accurate report.

Aside from timing of appointment being too close to the trial date, the Judge raised other concerns – mainly that there had been “anchoring” in respect of S’s expert’s work, most likely because she had to work at speed. Anchoring means that someone’s judgement, decisions or views are influenced by a reference point - usually the first piece of information they have seen (the “anchor”). Any new information is interpreted from that anchor and not seen objectively. 

Anchoring is subconscious. Perhaps a simple way of putting it is: “you can’t unsee what you have seen”. Here, the Judge believed that instead of considering and assessing matters in order to form an opinion independently and entirely based on her own experience and knowledge, S’s expert’s opinions were very likely (albeit, unknowingly) impacted by the prior experts’ reports. Even though there were some areas in S’s expert’s report where she took a different view to the earlier experts, the Judge still found her evidence to have been influenced by her colleagues’ earlier work (the anchor). 

An interesting speech about the science of memory, given by Lord Justice Popplewell in November 2023 was referred to by the Judge in this case in the context of anchoring. For a link to the speech please click here. Popplewell LJ’s commentary is also very relevant to the limitations of factual witness evidence and the fallibility of memory. The Courts have been very alive to that in recent years and the Judge made some remarks on this in the Skykomish case too. 

Key takeaways

There were a few key factors that aggravated the turn of events here and S’s expert’s credibility. The key one being that S’s eventual expert had been appointed very close to trial. 

Choosing which expert to instruct and ideally not changing them, especially anywhere near to 12 months before trial is advised. If making a change is unavoidable, it is essential to be wary of the risk of anchoring taking place. Ideally the new expert will not use or even review the previous expert’s work, regardless of whether they are from the same organisation or not. 

Committing to the same expert from start to finish is the ideal approach in terms of getting the expert embedded in the case and removing any question of whether anchoring has happened. It also avoids running up extra expert costs, i.e. the cost of duplication of work by multiple experts. Although the general rule is that a winning party can recover costs from the unsuccessful party, recovering costs of multiple experts if changes were made would be difficult. Unless there was a fundamental change in the case which was not the party’s fault. Also, any proposed change of expert would need the Court’s permission.

If a party wants to change their expert at any time during a case, there will be scrutiny over why that is being requested, i.e. are they “expert shopping” for someone who will agree with their case or form a view that keeps the client happier, instead of giving their own independent opinion to assist the Court? 

Finally but crucially, it is important to note that for any proposed change of expert, as a condition to allowing the change, the Court is likely to order disclosure of all previous expert instructions and reports, as well as drafts and notes relating to these. This is another reason why changing experts is best avoided at any stage of a claim!