Expert Determination vs Expert Witness

01Who decides?

The simplest way to distinguish the roles is to ask who makes the decision. An expert witness gives an opinion; the court or tribunal decides. An expert determiner decides the issue referred to them. An arbitrator decides a dispute under the Arbitration Act 1996.

02The expert witness

An expert witness provides independent evidence to help the court or tribunal. In civil proceedings in England and Wales, the expert's duty is to the court and overrides any obligation to the party instructing them, under CPR Part 35. The expert may be appointed by one party or jointly, and may be questioned on their evidence.

03The expert determiner

Expert determination arises from a contract, such as articles of association or a sale and purchase agreement, which provides that an independent expert will decide a defined issue. The expert uses their own expertise and investigations, follows the procedure in the contract or agreed with the parties, and issues a determination that binds the parties to the extent the contract provides. Grounds for challenge are generally narrow.

04The arbitrator

Arbitration is a statutory form of dispute resolution with procedural protections and limited rights of challenge and appeal. An arbitrator must act judicially, giving each party a fair opportunity to present its case. A valuer may sit as an arbitrator in a valuation dispute if appropriately appointed and qualified to do so.

05Which is right for your dispute?

The contract often decides: if it contains an expert determination clause covering the issue, that process usually applies. Otherwise:

• Narrow technical disputes, such as a completion accounts adjustment, often suit expert determination
• Disputes involving contested facts, legal issues and witness evidence usually require a court or arbitration
• In court or arbitration, valuation evidence is given by expert witnesses