Commentary

Judgment in this case was given by Master Evan Bell, a previous Grange Conference speaker, and the author of ‘Judicial assessment of expert evidence’ in the Judicial Studies Institute Journal, 2: 55-96, 2010 (https://ie.vlex.com/vid/judicial-assessment-of-expert-847477374 ) which might usefully be read with this case summary. Master Bell’s 13-point framework, which he used when considering the expert evidence, is also a useful framework for experts to use when reflecting on their expert witness practice or that of another expert in a case-based discussion or peer review. His framework is also a useful one for expert witness training.

For surveyor experts, the case illustrates some very basic errors and it may therefore also be a useful case for expert surveyor witness training.   

Learning points:

•   Beware over-reliance on the subject’s account to the exclusion of documentary evidence.

•    An expert report is only as good as the assumptions on which it is based.

•    Where one expert’s methodology is more sound than another’s, that expert’s opinion may be accorded more weight.

•     It is rare for expert speculation to assist.  

•     Inspection or examination must be thorough

The case

Breach of contract to build a house.

Expert evidence

The evidence in the case began with expert evidence offered on behalf of each party by a quantity surveyor.

The evidence of both experts was “hot-tubbed”. Instead of the parties' experts giving evidence and being cross-examined on it individually, the experts were sworn in at the same time and gave their evidence on a particular issue one after another before counsel moved on to another issue. This option for expert witnesses, to give their evidence concurrently was introduced in England by CPR PD 35, para 11 under the April 2013 Jackson Reforms. In Northern Ireland there is no statutory provision allowing such a practice and it is adopted under the inherent jurisdiction of the court to regulate its own procedure. The adoption of this practice both saves time and is particularly useful because it allows counsel and the court to hear the experts’ answers to the same questions shortly after one another rather than perhaps days or weeks apart. 

Both experts initially produced written reports. Prior to the hearing there was a meeting of the experts and they produced a Scott Schedule setting out the various items of work which the plaintiff was claiming for, the value being claimed for that work, whether the defendants’ expert agreed or disagreed and why, and the valuation which the defendants’ expert argued for.

Expert evidence is no different from any other evidence. The trial judge may accept it, reject it, or accept some of it and reject other parts of it. The role of the trial judge is to scrutinise the evidence thoroughly and ascribe to it such weight as he thinks it deserves. It must be as influential in the overall decision-making process as it deserves: no more, no less. There are many relevant judgments regarding expert witnesses and how their evidence should be approached, but it is widely acknowledged that one of the most important of these is a judgment by Sir Peter Cresswell in National Justice Cia Naviera SA v. Prudential Assurance Co. Ltd (The Ikarian Reefer) [1993] 2 Lloyd’s Rep 68. When it comes to assessing expert evidence, there are a number of factors which courts will often use in reaching conclusions as to whether an expert view is worthy of being relied upon. Certain of the criteria are interrelated and overlap. No single criterion is determinative. Some of the criteria are particular to expert evidence alone; others are used to assess the weight of all witness testimony. Those factors may include:

i.          The quality of the expert’s investigation 

           ii.          The correctness of the expert’s factual premises and underlying assumptions

          iii.          The soundness of the expert’s methodology

           iv.          The quality of the expert’s reasoning

            v.          The scientific validity of the expert’s conclusions

           vi.          The expert’s qualifications and reputation

          vii.          The objectivity of the expert

          viii.          Any bias demonstrated by the expert

            ix.          The context of all the other evidence

              x.          The expert’s performance under cross examination

             xi.          Any changes of opinion by the expert

            xii.          Whether the expert strays outside their field of expertise

            xiii.          The demeanour of the expert

The Master considered the evidence of both experts within this framework of consideration.

The Master began by addressing the expert evidence in general terms. He was not impressed by the evidence of Mr N. His underlying assumptions were sometimes incorrect. For example, in relation to the roof slates, he told the court that he had assumed that the slates would be put on and therefore claimed an amount for their installation. He made that assumption because the plaintiff had told him that he was about to do it, However the plaintiff did not affix the slates. During cross-examination Mr N had to concede that he had therefore assessed and included in his valuation of what was owed to Mr McBride, work which Mr McBride merely said that he intended to do. In his report Mr N wrote on a number of occasions “Client states done by others.” His opinion was therefore sometimes based not on what he himself witnessed but simply on what he had been told by the plaintiff. This undermined the weight that the Master could attach to his evidence. Another weakness in Mr N’s evidence was that, in attempting to reach an assessment of what might be owed to the plaintiff, Mr N did not carry out an actual inventory of materials on site.

In deciding what weight to accord expert evidence, a trial judge must take into consideration whether the methodology which an expert has employed is flawed. Where one expert’s methodology is more sound than another’s, that expert’s opinion may be accorded more weight. In this case there was a significant difference in the methodologies adopted by the experts. Mr N’s methodology left a very great deal to be desired. An example of this was in terms of his assessment of the amount of hardcore which had been provided by the plaintiff. His approach was to measure the section of ground on which there was hardcore and then simply to accept the word of Mr McBride that the hardcore had a particular depth. He did no sampling to check that what the plaintiff had told him was objectively true. Neither did Mr N look for proof of the purchase of a particular quantity hardcore, assuming that it may have been obtained in a cash sale.

Another example of Mr N’s flawed methodology was in relation to the external walls. Mr N told the court that he had made an assumption from the drawings that certain insulation work had been done (ie on the basis that it should have been done if Mr McBride had followed the plans with regard to the work he was supposed to do). The work, however, had not been done and Mr N did not check so as to verify for himself (and the court) that it had been done. His evidence at one point was that he had priced the job by the drawings and not by what he saw with his eyes. A further example of Mr N’s lack of diligence in methodological approach was in respect of the matter of whether cavities had been closed. Mr Lynch gave evidence that the closing of wall cavities had not been properly done and that the fire regulations in house building required that cavities be closed off by the use of a board. Mr N had to admit in his evidence that he had not inspected the cavities properly and had therefore to reduce his estimate of what was owed to Mr McBride by taking out the cost he had included for the closing of the cavities. Another consequence of Mr N simply working from the plans for much of his assessment was that he failed to observe that what should have been Quinn Lite Inner Block Leaf was not in fact the material used. Mr Lynch could tell this simply by observing the texture. Again, Mr N had to reduce what Mr McBride was claiming.

Further, in some instances, Mr N’s evidence appeared to be less of an expert conclusion and more a case of mere speculation. For example, in relation to the matter of insulation, the item in question was covered up and therefore difficult to inspect. Mr McBride told him that insulation had been laid on top of the joists. Mr N observed a black line in a photograph and his evidence to the court was “I thought that might be it.” On that basis he included a cost of £1,224.25 in his calculations for insulation.

As a result of Mr N’s approach to methodology the Master had no assurance that many of his conclusions were correct. By comparison, Mr Lynch approached matters in a much more formal way and looked for confirmatory documentary evidence where possible. For example, Mr Lynch sought documentary evidence from the plaintiff that a particular quantity of hardcore, said to have been obtained by the plaintiff, had in fact been purchased.  He also gave evidence that, in his experience, the site would not have required the amount of hardcore which Mr McBride was claiming for.

A significant evidential problem in the task of assessing the evidence of the parties, both expert and non-expert, was the inadequacy of the documentary evidence. Mr Lynch was critical of the lack of proper invoices provided by the plaintiff in respect of materials allegedly purchased by him. He noted, for example, that quarries normally provided invoices and that Mr McBride did not possess such invoices. The experts also differed significantly in their approach to the little documentary evidence which did exist. One of the invoices offered by the plaintiff was said to relate to the hire of a power washer. However there was nothing on the face of the invoice to indicate that it was for the hire of a power washer. Mr N, believing the word of his client, accepted it as genuinely having been for the hire of a power washer. Mr Lynch did not.

The weakness in the plaintiff’s claim was apparent from the very start of the expert evidence. The initial position of Mr N was that his client could legitimately charge £72,598 for the work done. Mr Lynch’s position was that the value of the work and purchase of materials amounted to £37,096. After a meeting of the quantity surveyors, Mr N was obliged to shift his calculation downwards to £65,279. This was prior to the major flaws in Mr N’s evidence being exposed by counsel.

The defendants’ counsel was predictably critical of Mr N’s evidence, describing him in his final submissions as “demonstrably an incapable and incompetent witness”, and arguing that his evidence was so poor that the court should reply solely on the evidence of Mr Lynch. The Master had to agree with that view. In terms of an overall assessment of the expert witness evidence offered on behalf of the plaintiff, the Master had to be highly critical of the quality of Mr N’s investigation, the correctness of his factual premises and underlying assumptions, and the soundness of his methodology. While on the face of matters he appeared to be a competent professional, he was exposed as not having been fit to have been put forward as an expert witness.

Although Mr N signed an expert witness declaration at the end of his report, it was clear that he did not abide by its terms. Paragraph 9 of the declaration states:

“I have not, without forming an independent view, included or excluded anything which has been suggested to me by others, including my instructing lawyers.”

Mr N’s evidence was clear that he had accepted the word of Mr McBride as regards what work had been done without objectively checking whether that was the position.

Essentially Mr N had only the vaguest idea of the role of an expert witness in court. He appeared to have had no training in the role of an expert witness. Such training is available from many sources including the Royal Institute of Chartered Surveyors. Indeed, the Royal Institute even publishes on its website a practice statement and guidance document on the subject of surveyors acting as expert witnesses. The quality of this document could be anticipated by the fact that the fourth edition of the guidance has a foreword written by Lord Neuberger, the former President of the Supreme Court.

By comparison, Mr Lynch’s methodology was far superior to Mr N’s. He did not simply go by the drawings but rigorously inspected the build on site and sought documentary evidence where possible.