Independence and conflicts in appeal evidence

Expert witness independence planning appeal questions come down to a single proposition: your duty to the inspector outranks your duty to the client who is paying you. That is the rule in the professional codes, it is what the Planning Inspectorate expects a proof of evidence to reflect, and it is the reason a proof has to contain the opinion you actually hold rather than the opinion the appellant would prefer.

Most of the difficulty is not about dishonesty. It is about the ordinary pressure of a case where you have been advising for two years, you drafted the application, and the strongest available argument is one you have private doubts about.

The duty owed when giving evidence

A witness at an inquiry gives evidence of opinion. The value of that evidence to the inspector depends entirely on whether it is the witness's own opinion, reached independently and stated fully.

The RTPI Code of Professional Conduct requires members to act with competence, honesty and integrity, and not to make statements contrary to their professional opinion. The RICS practice statement on surveyors acting as expert witnesses puts the point in the same way, adding that the duty to the tribunal overrides the duty to the client where they conflict. Both also require conflicts to be identified and disclosed.

The practical test is simple and uncomfortable. If you would give a different answer to the same question in a different case for a different client, on the same facts, the opinion you are offering is not independent.

None of this means you cannot advocate. It means the advocacy belongs to the advocate, and a proof of evidence that reads like a closing submission tells the inspector how to weigh it.

Declarations expected in a proof of evidence

Set the declarations out at the front, in plain terms, and keep them short.

What a proof normally states: your qualifications and experience relevant to the issues, the scope of your instructions, what you were asked to do and what you were not, the facts and assumptions you were given rather than established yourself, any part of the evidence prepared by someone else with that person named, and a statement that the opinions expressed are your true and complete professional opinions.

Also state your involvement in the scheme before the appeal. If you wrote the Planning Statement, negotiated with the officer and attended the committee, say so. Concealing it achieves nothing, because the council's advocate will have the application file, and disclosure removes the point from cross-examination.

Where you were given an assumption you cannot verify, for example a viability input or a survey conclusion from another discipline, attribute it. Then the inspector knows whose evidence carries that point, and if it falls, only that part of your evidence falls with it.

Acting for a client and remaining objective

Three habits keep the two things apart.

Write the weaknesses down early, in a note to the client, before the proof is drafted. A witness who has already articulated the difficulties is far less likely to be surprised into a concession under cross-examination.

Separate fact from opinion on the page. Facts are agreed in the statement of common ground or evidenced in appendices. Opinions are yours and should be labelled as such. A proof that blends them invites the question of which is which.

And answer the question the policy asks rather than the question you can answer well. Where the development plan requires a judgement on harm, reach one, and say how you weighed it. Evidence that avoids the central judgement is worse than evidence that reaches an unhelpful one, because the inspector still has to make the judgement and now has no assistance.

The dual role question comes up constantly in smaller appeals. Acting as both advocate and expert witness in the same case is something the professional guidance advises against, and in a written representations appeal the distinction is blurred by the format. Where the case is significant, separate the roles.

Previous involvement in the same scheme

Previous involvement is usually not a disqualifying conflict. It is a matter to disclose, and occasionally a reason to decline.

The clear-cut problems are these. Having previously advised the local planning authority on the same site, where you hold information from that role. Having been the case officer or a decision-maker on the application. Having a financial interest in the outcome beyond your fee, including a success fee or an interest in the land. Acting against a former client on the matter you advised them on.

The harder cases are softer. A practice that advises the appellant and has a separate team advising an objector on an unrelated site nearby. A witness who has published a strong view on the policy question at issue. A consultant whose fee is largely contingent on further work if the appeal succeeds.

The answer in the soft cases is disclosure plus a judgement about whether your opinion can be, and be seen to be, independent. Where you cannot answer that comfortably, decline. The professional codes treat a failure to disclose as more serious than the conflict itself, and the same principle runs through competence questions generally, as we set out in what competent person means in planning legislation.

Where a conflict or a change of view emerges mid-inquiry

It happens. A document is disclosed, a witness for the other side produces data you did not have, or your own further analysis undermines a paragraph of your proof.

The obligation is to correct it. In practice that means telling your instructing solicitor or agent immediately, agreeing how the correction is made, and putting it in writing to the inquiry, either in a supplementary note or orally at the start of your evidence. An inspector who hears a witness correct their own proof treats the rest of that proof more favourably, not less.

Do not let the correction be extracted in cross-examination. A concession made under pressure on point four undermines points one to three, whereas the same concession volunteered in opening changes almost nothing.

Where a conflict of interest emerges mid-inquiry, disclose it to the inspector through the advocate at once and take instructions on whether you can continue. Continuing without disclosure is the version of this that ends in a professional conduct complaint.

Costs consequences of unreliable evidence

Costs at appeal are awarded for unreasonable behaviour, and the national guidance on appeals sets out the categories. Evidence is implicated in several of them.

The situations that attract applications include introducing substantial new evidence late so that the other party cannot respond, pursuing an appeal on grounds that the evidence does not support, failing to produce evidence to substantiate a case on a matter the party knew would be in issue, and withdrawing from a position at a late stage after the other side has incurred cost answering it.

The reputational effect is separate and longer-lasting. Inspectors write decisions that name what they made of a witness's evidence, those decisions are public, and the same inspectors hear other appeals.

Where a reviewer signs off specialist work that will be tested at appeal, the review needs to be a real one. The professional directory is the route to reviewers who take that responsibility, and the competence expectations for financial evidence in particular are covered in viability assessment competence and RICS standards.

Preparing a witness for cross-examination

Preparation is legitimate. Rehearsing answers you do not believe is not.

What helps: a thorough read of your own proof against the other side's, a list of every paragraph you would find hardest to defend, agreement in advance on what you will concede if pressed, and a clear understanding of the boundary of your expertise so that you can decline a question outside it rather than guessing.

What to avoid: answering questions outside your discipline, speculating on matters of law, arguing with the advocate, and defending a position you no longer hold because it is in your proof. A witness who says that a point in their proof now looks overstated loses that point and keeps their credibility.

One honest observation from practice: the most damaging moment in cross-examination is rarely a factual error. It is the witness who will not accept an obvious proposition, because the inspector then discounts everything that follows.

This is general guidance, not legal advice. Check the position with your local planning authority or a qualified professional before relying on it. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.