Trial strategy when the opposing expert has a conflict of interest

Australian litigators often encounter a deceptively simple problem: the opposing expert has been retained by the other side, and the document trail suggests a connection the report never explains. A prior retainer, lender relationship, contingent fee or shared financial interest can place an expert’s independence in issue. The critical question is not whether the witness has been paid. It is whether a competing loyalty or interest is material, undisclosed and capable of colouring the opinion.

Conflict analysis is a trial strategy rather than merely an ethics exercise. In federal and state litigation, the court ordinarily asks whether the opinion is admissible, relevant and reliable, then considers weight if the foundation is sound. A conflict may affect any of those questions, but it does not automatically disqualify an expert or guarantee a win. Success comes from converting an abstract suspicion into a precise, provable and procedurally fair attack.

Find and classify the conflict early

Start with a conflict inventory, not a cross-examination script. Identify each connection between the expert and the parties, witnesses, funding entities or organisations likely to benefit from the opinion. Separate current financial interests from past retainers, and separate those from family, friendship or reputational ties. “Previously worked for” is a fact; “the prior work supplies data now relied upon” is a conflict with possible evidentiary consequences.

The search should extend beyond the report. Compare the expert’s curriculum vitae, publications, prior testimony, invoices, retainer terms, conflict declarations and disclosed relationships with the evidence and chronology. In Sydney and Melbourne, experts are often drawn from university departments, boutique forensic firms, national accounting networks, insurers and litigation funders. That local market makes institutional relationships common; it also makes disclosure documents especially important.

Record the date, duration and nature of every relationship. A short consulting engagement several years earlier may carry little weight, while an ongoing success fee or confidential access to the client’s records may be central. The difference lies in materiality, and materiality is easier to assess before memories fade, files are closed or the trial consumes every available hour.

Distinguish partiality from a merely wrong opinion

Not every disagreement is evidence of bias. An expert can disagree with the case advanced by the other side and still reach a balanced conclusion. Likewise, an adverse opinion does not become suspect merely because the witness earns fees from the party calling them. Trial lawyers who treat every robust conclusion as proof of corruption lose credibility with the court and may invite a finding that the challenge was tactical rather than substantive.

The useful distinctions are narrower. Ask whether the expert knowingly omitted a material connection, whether the connection affected the data selected or assumptions adopted, and whether the opinion changed once contrary information was considered. Candour matters: an expert who volunteers context and explains why it does not undermine the opinion may withstand scrutiny. Concealment, inconsistent answers and a failure to correct an inaccurate disclosure present a different concern.

Under Australian evidence law, bias commonly becomes a question of weight rather than automatic exclusion, although serious confidentiality or independence failures can support a stronger challenge. The court should be given a focused submission connecting the relationship to a specific part of the opinion. General assertions of “conflict” or “bias” are easy to dismiss. A supported allegation explains what the expert knew, what the expert did not disclose, and why the evidence supplied by the party cannot safely be accepted without qualification.

Examine money, clients and intellectual loyalties

Financial conflicts require the closest scrutiny because they are usually verifiable. Review whether fees are contingent on success, whether the expert holds investments or loans connected with a party, whether commissions or referral fees exist, and whether billing has been described accurately. Success fees are not inherently improper, and some jurisdictions permit them only in defined circumstances. The strategic point is that their presence, structure and disclosure can be explored without suggesting that payment alone proves bias.

Prior and current client relationships create a second category. An expert may have advised the party on the very issue now in dispute, received confidential material relevant to the opinion, or testified for an aligned interest in earlier litigation. Confidentiality can make this more serious than a public disagreement because the court must know whether the opinion is genuinely the witness’s own. If the relationship is disclosable and the earlier material could influence the evidence, seek the underlying records through proper disclosure or a court order rather than through an informal approach to the expert.

Intellectual loyalty is harder to see but not impossible. Does the expert consistently champion one side of a contested question, rely on a narrow methodology that excludes decisive information, or describe contrary authority as unsound without engaging it? Such patterns may show allegiance, methodological bias or commercial dependence. They must still be tied to objective material. The evolution of evidence rules in United States federal courts offers comparative background on how formal admissibility and practical reliability have diverged, although it is not authority in an Australian court.

Build a defensible documentary record

The best challenge is documentary. Audit emails, project files, data-room records and document-management metadata lawfully available for instructions to the expert, comments on draft opinions, fee discussions and changes after counsel reported weaknesses. A useful warning about internal business documents explains how routine messages can expose litigation risk. Although that discussion is framed around United States practice, the practical lesson travels well: an email that appears ordinary in isolation may reveal who supplied information, what the expert was asked to assume and whether an opinion was shaped to suit litigation.

Preserve the record in context. An incomplete extract can be misleading, and material held by a represented party may be subject to legal professional privilege. Use appropriate disclosure requests and, where necessary, court applications. If privilege is asserted, seek inspection or in camera review where the forum permits it. Keep original files and a chronology of custodial sources. If the central allegation is that an expert was coached, the relevant difference between a recorded request and counsel’s proper case preparation must be explored fairly.

Then build an index that links each document to a proposition. Label the retained relationship, identify the undisclosed interest, quote the relevant instruction and explain the consequence for methodology. A court is more likely to act on five documents that establish a coherent problem than on fifty messages that merely show frequent contact. For example, an invoice can establish payment; an email discussing a disputed assumption can establish influence; together with inconsistent testimony, they may justify restricting the weight given to the opinion.

Use court directions to contain the issue

Raising a conflict at trial without notice can look like ambush, particularly after a familiar Australian morning has moved from court attendance to a hurried conference-room coffee before the witness is called. Raise the issue at the earliest practical stage, disclose the documents supporting it and invite the other side to respond. Depending on the forum, seek an expert conference, directions on disclosure, permission to review the material or a direction that the expert address the issue in evidence.

Proceedings in the Federal Court turn on the Federal Court of Australia Act 1976, the Federal Court (General) Rules 2013 (Cth) and applicable expert evidence directions. State proceedings turn on their own laws, including the Uniform Civil Laws and Evidence Act 1999 in New South Wales, the Evidence Act 1995 in Queensland and the Evidence Act 2008 in Victoria. The procedural route may differ, but all require a fair opportunity to be heard. A specific notice of intended issue is usually more effective than a general demand that the witness be removed.

An objection is not the only available remedy. The parties can agree to instruct a joint expert, ask the court to nominate a suitable expert or use a concurrent expert process to narrow the disputed issue. Sometimes the conflict can be neutralised by allowing the opposing expert to answer direct questions and disclose the relationship in open court. The aim is to improve the reliability of the decision, not merely to disqualify a witness who gives the other side useful evidence.

Cross-examine the opinion and the disclosures

Preparation should proceed on two tracks. First, test the opinion itself: qualifications, scope of expertise, source material, assumptions, calculations, consistency, treatment of counter-evidence and reliance on earlier work. Second, test the conflict: what the witness knew about each relationship, when it was disclosed, what was asked, what was not said and whether any confidential information affected the conclusion. Questions should establish facts, not deliver accusations in the form of questions.

Comparators can help refine the themes. European legal commentary offers a broader external perspective on evidence and procedure, but the decisive material will come from the Australian record and the witness’s own answers. The trial judge should be able to follow the sequence from relationship to disclosure to consequence. Avoid personal attacks, speculative claims and attempts to communicate privately with a witness represented by the other side; those tactics can obscure a valid concern and create their own conduct problems.

Before the hearing, the team should mark the passages in the expert’s report that each document undermines. Prepare the question that opens the relationship, the question that fixes its timing, the question that tests candour and the question that connects it to weight. If the answers contradict the report, narrow the submission to the contradiction. If they explain the report, move on. Disciplined cross-examination is not an assault on the witness; it is a controlled demonstration of whether the opinion is independent enough to bear the weight sought for it.

Before accepting an adverse expert report, order a focused conflict audit covering retainers, invoices, declarations, prior testimony, institutional ties and the source material behind the opinion. Preserve the documents, identify the governing procedural rules and formulate the precise consequence sought. That preparation turns a vague suspicion into a manageable trial issue.

Make conflict review a standard step in every Australian matter involving expert evidence, from a commercial dispute heard in Melbourne to urgent federal litigation in Sydney. Ask the right questions early, disclose what is material and test the connection against the opinion. Used with care, the conflict becomes neither a personal vendetta nor an empty accusation; it becomes a disciplined route to evidence the court can trust.