Related Sector: Expert Witness

The recent Family Court case of Gallagher v Gallagher provides key commentary on the issue of expert impartiality. In particular, the judge found that the husband’s expert had effectively become part of the party’s legal team, acting in manner and mentality as an ‘’advocate’’ rather than an independent expert.


This hearing was in relation to a wife’s application for financial remedies dated 14 April 2020.

On 6 November 2020, the wife made a Part 25 application for the instruction of experts, including a forensic business accountant, a tax accountant, and several surveyors.

At the Case Management Hearing on 25 May 2021, Holman J gave his permission for two experts: Ms Longworth for the wife and Mr Singleton for the husband, to meet and produce a joint statement as to the husband’s business interests.

Expert Impartiality

In reviewing the conduct of the husband’s expert, Mr Justice Mostyn relied on excerpts from two key pieces of commentary.


The area of expertise in any case may be likened to a broad street with the plaintiff walking on one pavement and the defendant walking on the opposite one. Somehow the expert must be ever mindful of the need to walk straight down the middle of the road and to resist the temptation to join the party from whom his instructions come on the pavement. It seems to me that the expert’s difficulty in resisting the temptation and the blandishments is much increased if he attends the trial for days on end as a member of the litigation team.Some sort of seduction into shared attitudes, assumptions and goals seems to me almost inevitable.”

Thorpe LJ in Vernon v Bosley (No 1) [1996] EWCA Civ 1310


[Lord] Hamblen said witnesses should refrain from becoming an advocate themselves and give evidence in such a way that you would not know which side has instructed them. ''There is nothing more fatal to the acceptability of an expert’s evidence than the questions of independence and impartiality,'' he said. ''It will taint all [and] it is therefore vital to avoid any hint of partiality.''

"It is counsel’s job to argue a case – that is not the role of an expert. If you give evidence in an argumentative manner that will undermine your independence."

‘Partisan experts can be fatal, Supreme Court justice warns’ – Law Society Gazette (20 May 2022)

The husband’s expert

Mr Justice Mostyn considered Mr Singleton, the husband’s expert to be a ‘’highly proficient, knowledgeable, intelligent and articulate accountant’’ who ‘fully immersed himself’ in his instruction.

The judge also acknowledged the limits of expert impartiality, stating that:

‘’some might say that the forceful judicial demands for impartiality are tinged with unworldliness. It seems to me to be not unlikely that subconscious forces may well incline an expert, who is being handsomely paid by one of the parties, to give evidence favourable to that party.’’

In spite of this though, he agreed with the wife’s barrister about to Mr Singleton’s conduct. He stated that Mr Singleton lacked the impartiality required as an expert witness, and instead acted in a ‘‘strategic defensive manner’’ that had ‘’all the hallmarks of the mentality of an advocate’’. 

The judge cited the following as evidence of this:

1)      Mr Singleton’s attendance throughout the two-day private Financial Dispute Resolution hearing, which was ‘’highly suggestive of de facto membership of the husband’s team.’’

2)      Mr Singleton’s email to one of the husband’s witnesses, a Mr Kerins about a possible comparable transaction, stating ‘’it is a great comparable and we can argue that the contracts…’’ This highlighted his perceived membership of the husband’s team.

3)      His written evidence which put forward figures, which were ‘as low as he could tenably go without failing off the spectrum altogether’’.

4)      Mr Singleton’s interruptions of Ms Longworth were ‘forthright, abrasive and adversarial, even degenerating on one occasion.’’


As this was a financial remedy hearing, the judge viewed Mr Singleton’s evidence in light of his perceived bias. He disregarded some of the expert’s evidence (point 3 above) but allowed others that he felt had been accurately recorded.


This family law case provides invaluable commentary for expert witnesses as to the manner of conduct, language and attitude that could be perceived by a judge to be lacking in impartiality.

Whilst experts may be instructed by (and paid by) a party, it is of utmost importance that they do not consider themselves to be part of that party’s legal team. Their duty and obligation remain wholly to the court (for reference: Rule 35.3, Civil Procedure Rules, Rule 25.3, Family Procedure Rules and Rule 19.2, Criminal Procedure Rules).  

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