Tribunal-appointed expert in arbitration: questioning and counter-expertise

A tribunal-appointed expert can clarify a technical issue in arbitration. Section 601 of the Austrian ZPO gives the parties practical participation rights: they may ask questions, have their own experts give evidence on disputed issues and submit their own expert reports. These rights should be prepared as soon as the expert report and its underlying material are available.

This article addresses a tribunal-appointed expert. It focuses on reviewing the assignment, preparing questions and developing a technically grounded counter-expertise. A party expert report has a different procedural function because it is prepared on a party’s instructions.

A broad statement that the report is wrong rarely provides a useful response. The relevant issues are the tribunal’s questions, the data set, the method, open assumptions and the effect on the claim or defence.

What section 601 ZPO allows in arbitration

Section 601 ZPO links the expert report to defined questions set by the arbitral tribunal. The tribunal may appoint one or more experts. It may also require the parties to provide relevant information or to produce or make available documents and items needed for an examination.

The second paragraph is central to the response. If a party requests the expert’s attendance at an oral hearing, or the tribunal considers attendance necessary, the expert must attend. The parties may ask questions and have their own experts give evidence on the disputed issues.

Review the tribunal assignment and questions

Start with the appointment decision or procedural order. Which questions were put to the expert? Is there a cut-off date, a defined data set or a methodological instruction? A report may be technically careful and still miss the decisive issue if the assignment was too narrow or unclear.

Compare each conclusion with the assignment. Mark whether the expert answers a factual question, adopts an assumption or moves into a legal assessment. The tribunal decides legal issues. Questions should therefore test or clarify the technical reasoning, data and calculations.

Prepare questions for the expert

Effective questioning follows the structure of the report. Organise questions by data, method, assumptions, calculations and conclusion. Ask which document supports a finding, what uncertainty remains and whether another starting date or data source would change the result.

Each question should serve a defined disputed issue. For a quantity calculation, the measurement date, method and comparator belong together. For costs, review performance, price basis, allocation and calculation separately. This makes the later assessment easier for the tribunal.

Use own experts and counter-expertise

Section 601 ZPO generally gives each party the right to submit its own expert report. A counter-expertise should focus on the disputed issues. It does not need to reproduce the entire tribunal report when one assumption, calculation or conclusion is decisive.

The own technical opinion should address the tribunal’s assignment expressly. For each objection, identify the relevant passage, the different data or method and the effect on the conclusion. This shows whether the counter-expertise identifies an error, uncertainty or a defensible alternative assumption.

Review independence and possible challenge

The identity of a tribunal-appointed expert also requires review. Under Article 23 of the Vienna Rules, the rules on challenging arbitrators apply correspondingly to experts appointed by the tribunal. The tribunal decides the challenge. A challenge therefore needs concrete facts concerning independence or impartiality and should follow the applicable procedural route.

That issue is separate from technical criticism. A conflict does not establish that every calculation is wrong. Conversely, a different technical view does not by itself prove bias. Each line should be supported by its own facts and procedural request.

Observe the right to be heard and objections

Article 28 of the Vienna Rules requires fair treatment and a right to be heard at every stage. Article 30 provides that the parties must have an opportunity to know the result of evidence and comment on it. This frames the response to the report, but it does not replace a focused technical analysis.

When a party learns of a breach of the Vienna Rules or another applicable procedural rule, Article 31 requires an immediate objection to the tribunal if the party wants to preserve the right. Secure delivery of the report, the procedural order, the deadline and the response in a clear chronology.

Distinguish court assistance in evidence

Section 601 ZPO concerns the tribunal-appointed expert and participation within the arbitration. If a judicial act is required that the arbitral tribunal is not empowered to perform, a different route under section 602 ZPO may be relevant. The article on court assistance in arbitration explains that distinction.

A party expert report is another distinct evidential route. The article on the technical party expert report addresses a report commissioned by a party. This article concerns the response to an expert appointed by the tribunal itself.

Organise documents for questioning and response

The preparation file should contain the appointment decision, assignment, complete report, exhibits, raw data, calculations, measurement records, relevant contract documents and procedural orders. Add proof of service, the deadline for comments and the evidential strategy.

Mark each disputed technical issue together with its importance for the claim, defence or quantum. If a counter-expertise is needed, the own expert should receive the same material and state which data was unavailable. This makes differences between the reports comparable.

Common questions about tribunal-appointed experts

May I question an expert appointed by the arbitral tribunal?

Yes. Section 601 ZPO allows the parties to ask questions when the expert attends an oral hearing following a party request or because the tribunal considers attendance necessary. Questions should address the assignment, data, method and conclusions.

Can I appoint or present my own expert?

Yes. Section 601 ZPO generally permits each party to submit its own expert report and have its own expert give evidence on disputed issues. Any party agreement or specific procedural order must be checked.

When is a counter-expertise useful?

A counter-expertise is particularly useful when the tribunal report’s data, method, assumptions or calculations are decisive and technically reviewable. It should explain the disputed issues and their effect on the arbitration.

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Next step

Contract, arbitration clause, correspondence and deadlines should be collected. It can then be assessed whether negotiation, preservation or arbitration is central.