If you are involved in a property dispute heading towards court, a tribunal or arbitration, you will almost certainly hear the term expert witness. But what is an expert witness, exactly? This guide explains the role, what the rules in England and Wales require, what an expert witness report contains, and when a property dispute calls for a chartered surveyor in the role. Please note this article is general information only, not legal advice; take advice from a solicitor on your specific circumstances.
What Is an Expert Witness? A Clear Definition
An expert witness is an independent specialist who gives opinion evidence to a court or tribunal on matters within their field of expertise. That short definition contains two ideas that are easy to miss.
First, an expert witness gives opinion evidence. Ordinary witnesses may generally only tell the court what they saw, heard or did. An expert is permitted to interpret the facts, because some questions cannot be answered without specialist knowledge. Whether a crack indicates subsidence, whether a valuation fell within a reasonable range, whether a repair method was appropriate: these are questions of professional judgement, not simple fact.
Second, and most importantly, an expert witness is independent. Although one party usually instructs and pays the expert, the expert’s overriding duty is to the court or tribunal, not to whoever pays the fee. An expert who shades their opinion to help their client is not doing the job; they are undermining it, and courts deal severely with experts who act as partisans.
In property and construction matters, the expert is very often a chartered surveyor: regulated by the Royal Institution of Chartered Surveyors (RICS), with the technical knowledge to opine on building defects, valuations, boundaries, party wall matters and similar disputes.
Expert Witness vs Advocate vs Witness of Fact
It helps to see where the expert witness sits alongside the other people involved in a dispute.
- A witness of fact tells the court what they personally saw, heard or experienced — a neighbour who watched a wall being demolished, for instance. They describe events; they do not offer professional opinions.
- An advocate — usually a barrister or solicitor — argues one party’s case as persuasively as the rules allow. Advocacy is openly partisan; that is its proper role.
- An expert witness occupies the ground between the two. They give evidence, like a witness, but it is opinion evidence based on expertise — and crucially, they must not act as an advocate. An expert who argues their client’s case rather than giving their honest professional view is sometimes called a “hired gun”, and once a judge doubts an expert’s independence, their evidence loses much of its value and their client’s case suffers.
A related role is the expert adviser (or “shadow expert”): a specialist who advises a party privately on the strengths and weaknesses of a claim without giving evidence. The same person cannot comfortably wear both hats in one matter, so be clear at the outset which role you need.
CPR Part 35: The Rules Governing Experts in England and Wales
In civil litigation in England and Wales, expert evidence is governed by Part 35 of the Civil Procedure Rules (CPR), together with its Practice Direction and related guidance. The broad principles are worth understanding before you instruct anyone.
The expert’s duty to the court
CPR Part 35 makes explicit what we described above: the expert’s duty is to help the court on matters within their expertise, and this duty overrides any obligation to the person instructing or paying them. Expert evidence should be the independent product of the expert, uninfluenced by the pressures of litigation. Experts are expected to consider all material facts, including those that might undermine their opinion, and to say when a question falls outside their expertise or cannot be answered definitively on the available evidence.
The expert’s declaration and statement of truth
A report prepared for court proceedings must contain a statement that the expert understands and has complied with their duty to the court, verified by a statement of truth. That is serious: a false statement made without honest belief in its truth can expose the maker to contempt proceedings. This is one reason experienced experts are careful, measured and unwilling to say more than the evidence supports — exactly as it should be.
Court permission and proportionality
A party cannot simply turn up to trial with an expert. The court’s permission is required to rely on expert evidence, and the court controls how it is given: whether each party may appoint its own expert or a single joint expert should be used, whether evidence is written only, and which issues the experts should address. The court restricts expert evidence to what is reasonably required, keeping cost proportionate to what is at stake.
Similar principles apply in other forums — tribunals, arbitrations and adjudications have their own rules, but the expectation of impartial, competent opinion evidence runs through all of them.
What Does an Expert Witness Report Contain?
The report is the centrepiece of the expert’s work — many disputes settle on the strength of the reports alone, without oral evidence ever being given. A compliant report prepared by a surveyor will typically include:
- The expert’s qualifications and experience, so the court can judge their competence to opine on the issues.
- The instructions received — a summary of the material instructions on which the report is based.
- The factual basis — documents reviewed, inspections carried out, measurements taken and assumptions made, with facts clearly separated from opinion.
- The substance of the opinion — reasoned conclusions on each question asked, with the reasoning shown, not just asserted.
- A range of opinion — where reasonable professional views differ on an issue, the report should say so and explain why the expert holds theirs.
- Any qualifications — matters the expert could not verify, limits on the inspection, or issues outside their expertise.
- The declaration and statement of truth confirming compliance with the duty to the court.
A good report is written for an intelligent non-specialist: jargon is explained, photographs and plans are used where they help, and the reasoning can be followed step by step. Clarity is what makes a report persuasive.
Single Joint Experts vs Party-Appointed Experts
Expert evidence can be arranged in two main ways, and the difference matters when planning a case.
- A single joint expert (SJE) is one expert instructed jointly by both parties, reporting to both and owing the same duty to the court. Courts often favour this in lower-value or narrower disputes because it saves cost and avoids duelling experts; each party can put written questions to the SJE about the report.
- Party-appointed experts are separate experts instructed by each side, more common in higher-value or complex disputes where the issues genuinely admit a range of professional opinion. The experts will usually be directed to meet and produce a joint statement recording their agreements and disagreements.
Whichever route is taken, the duty of independence is identical. A party-appointed expert is not “your” expert in any partisan sense; they are an independent professional whose honest opinion forms part of your evidence — and they cannot and will not simply say what a client wants to hear.
When Does a Property Dispute Need a Surveyor Expert Witness?
Broadly, a surveyor expert is needed whenever the outcome of a dispute turns on technical questions about buildings, land or value. Common examples include:
- Building defects and construction disputes — where work is alleged to be defective or not in accordance with the contract, a construction expert witness can opine on workmanship, causation and the cost of remedy.
- Boundary disputes — disagreements over where a legal boundary lies often turn on measured surveys, historic plans and site features: the territory of a boundary dispute expert witness.
- Valuation disputes — where parties disagree about what a property is or was worth, for example in matrimonial, lease or tax contexts, a valuation dispute expert witness provides an independent opinion of value.
- Dilapidations — landlord and tenant disputes over repairing obligations at lease end frequently require a dilapidations expert witness to opine on the condition of the premises and the reasonableness of the claim.
- Housing disrepair — tenants’ claims concerning damp, mould and other defects in rented housing commonly rely on a housing disrepair expert witness to report on the property’s condition and likely causes.
- Party wall matters — where works to a shared or adjoining structure lead to damage claims, a party wall expert witness can address whether the works caused the damage and what remedy is appropriate.
- Professional negligence — where a surveyor is alleged to have missed serious defects or produced a flawed valuation, a surveyor negligence expert witness gives an opinion on whether the work met the standard of a reasonably competent member of the profession.
In each area the expert’s role is the same: an honest, reasoned, independent opinion on the technical questions, whichever way it cuts.
How Expert Witnesses Are Selected and Instructed
Choosing the right expert is one of the most consequential decisions in a technical dispute. In practice, solicitors and parties look for:
- Genuine expertise in the specific subject matter. A valuation dispute calls for a valuer; a defects claim calls for a building surveyor. The expertise must match the issues, not merely the profession.
- Professional standing — RICS membership, adherence to RICS guidance on surveyors acting as expert witnesses, and appropriate professional indemnity insurance.
- Experience of the expert role itself. Writing a Part 35-compliant report, attending experts’ meetings and giving oral evidence under cross-examination are skills in their own right.
- Independence. No prior involvement with the property, the parties or the transaction that could compromise, or appear to compromise, impartiality.
- Availability and clarity on fees. Court timetables are unforgiving, so the expert must be able to inspect, report and attend within the directions.
Instruction usually comes through a solicitor, though experts can be instructed directly. Good instructions set out the issues to address, provide the relevant documents, and do not attempt to steer the answer. It is sensible to ask a prospective expert for a preliminary view and a fee estimate before formal instruction.
Frequently Asked Questions
What is an expert witness report?
An expert witness report is a formal written document in which an independent specialist sets out their qualifications, the instructions received, the facts and assumptions relied on, and their reasoned professional opinion on the technical issues in a dispute. In civil proceedings in England and Wales it must comply with CPR Part 35, including a declaration of the expert’s duty to the court and a statement of truth. Many disputes settle once reports are exchanged, without a trial.
Who pays for an expert witness?
The instructing party is responsible for the expert’s fees in the first instance; where a single joint expert is appointed, the parties usually share the cost. At trial, the court may order the losing party to pay the winner’s reasonable costs, which can include expert fees, though recovery is discretionary and rarely complete. Experts must never be paid on a conditional or success-fee basis, as that would compromise their independence.
Can any surveyor act as an expert witness?
The court decides whether a witness is qualified to give expert evidence; there is no single statutory register. In practice, an effective expert needs deep, current expertise in the specific subject matter, familiarity with CPR Part 35 and the professional guidance for surveyors acting as expert witnesses, and the ability to write clear reports and withstand cross-examination. A surveyor without that combination may do more harm than good, so choose carefully.
Speak to a Chartered Surveyor About Expert Witness Services
This guide is general information, not legal advice — always consult a solicitor about your own dispute. If your case turns on building defects, boundaries, valuation, dilapidations, disrepair, party wall matters or alleged surveyor negligence, our RICS chartered surveyors provide independent, CPR Part 35-compliant expert witness reports across London. Request your free quote and we will confirm quickly whether your case falls within our expertise.