Red Flags When Selecting an Expert
- No active professional practice in the relevant discipline
- Cannot provide examples of CPR Part 35 or IBA Rules compliant reports
- Unwilling to confirm independence and duty to the court in writing
- No professional indemnity insurance
- Attempts to opine outside their area of expertise across multiple disciplines
- Fee estimate significantly below market without explanation
- No prior court, tribunal, or arbitration testimony experience
Single Joint Expert (SJE) vs Party-Appointed Expert (PAE)
Under CPR Part 35, the court may direct that evidence on a particular issue is to be given by a Single Joint Expert (SJE) instructed jointly by the parties, or by party-appointed experts (PAEs) instructed separately by each side. The choice has significant implications for cost, strategy, and the quality of expert evidence presented to the court.
A Single Joint Expert is instructed by both parties under a joint letter of instruction and produces one report addressing the agreed issues. The SJE model reduces the cost of duplicate expert analysis, limits the risk of polarised expert evidence, and is increasingly favoured by courts in cases where the technical issues are capable of objective analysis. Either party may ask questions of the SJE in writing, and the SJE may be cross-examined at trial. The court may also permit a party to instruct their own expert where the SJE's report is disputed, subject to cost consequences.
A Party-Appointed Expert is instructed by one party alone and provides independent evidence within their discipline. PAEs are appropriate where the issues are genuinely contested, where each party needs independent analysis to assess settlement prospects, or where the court has not directed a joint expert. In complex multi-discipline disputes, it is common for each party to appoint separate experts in each relevant discipline, for example, separate forensic accountants, digital forensics experts, and quantum experts on each side.
Regardless of whether the expert is an SJE or PAE, CPR Part 35 applies equally: the expert's primary duty is to the court, the report must be objective and independent, and the expert must cooperate in narrowing issues through joint meetings and joint statements where directed.
Preparing for Concurrent Evidence (Hot-Tubbing)
Hot-tubbing, formally known as concurrent evidence, is a procedure increasingly used in UK courts and international arbitration where experts from both sides give evidence simultaneously before the judge or tribunal, rather than in the traditional sequential format of examination-in-chief followed by cross-examination.
In a hot-tubbing session, experts are sworn in together and the judge or arbitrator directs the discussion, asking questions, probing areas of agreement and disagreement, and inviting experts to respond to each other's opinions in real time. This format allows the tribunal to directly compare expert evidence, identify the true areas of dispute, and resolve technical questions more efficiently than traditional cross-examination.
Hot-tubbing is particularly common in the Technology and Construction Court (TCC) for quantum and delay disputes, in competition proceedings before the Competition Appeal Tribunal (CAT), and in international arbitration under ICC, LCIA, and ICSID rules. It is especially valuable in digital forensics cases where technical evidence is highly specialised, and in complex construction disputes where multiple disciplines, quantum, delay, and forensic engineering, are engaged.
Preparation for hot-tubbing requires experts to have participated in joint meetings, produced a joint statement identifying agreed and disputed issues, and be ready to explain their methodology and opinions clearly and concisely under direct questioning from the tribunal. Solicitors should ensure their forensic experts are experienced in concurrent evidence procedures before instructing them for cases where hot-tubbing is likely to be ordered.