An Expert Witness’s Proper Approach in Testimony

In recent issues, Hearsay has included a number of pieces concerning the proper approach by court experts in furnishing court testimony. Despite all that has been written in recent years in this space, some experts portray (often despite good intentions) more of an argumentative or combative, rather than impartial, approach to their task. In Metricon Homes Pty Ltd as Trustee for Metricon Homes Unit Trust v Lipari [2024] NSWSC 566 (16 May 2024), Nixon J made criticisms of the form of the evidence an expert building witness, albeit ultimately accepted the evidence adduced as impartial in character. Such criticisms, in broad terms, serve to inform the proper approach which an expert ought adopt in framing responses in primary reports, conclave reports and viva voce evidence respectively. First, be responsive and unequivocal in expression of expertise and opinion. Second, be courteous, albeit frank, in any critique of a disparate expert view. Third, refrain from descending to plainly irrelevant and inadmissible facts, including comparisons with other complex scenarios, or previous experience with the work of the involved parties. To do otherwise could well diminish the reliance the court places on the expert’s opinions in arriving at the adjudication. The court wrote:

[59]  I accept a number of the criticisms made by Metricon and Zanuttini regarding Mr Camenzuli’s evidence.

[60]  First, Mr Camenzuli’s oral evidence was, at times, discursive, repetitive and non-responsive, making it difficult to identify the opinions being advanced by him, the basis of those opinions, and whether those opinions were based on specialised knowledge.

[61]  An example is set out below. It is necessary to provide some background to place this evidence in context. The Contract between Mrs Lipari and Metricon annexed a CSIRO publication entitled “Foundation Maintenance and Footing Performance: A Homeowner’s Guide”. It included the following information on “Seasonal swelling and shrinkage of soil”:

All clays react to the presence of water by slowly absorbing it, making the soil increase in volume (see table below). The degree of increase varies considerably between different clays, as does the degree of decrease during the subsequent drying out caused by fair weather periods. Because of the low absorption and expulsion rate, this phenomenon will not usually be noticeable unless there are prolonged rainy or dry periods, usually of weeks or months, depending on the land and soil characteristics.

The swelling of soil creates an upward force on the footings of the building, and shrinkage creates subsidence that takes away the support needed by the footing to retain equilibrium.

In his report of July 2023, Mr Camenzuli had stated that “it is accurate to conclude that we have undergone a number of shrink and swell cycles over the last 5 years”. In their joint report, Mr Hartcher and Mr Keighran also referred to the “seasonal weather patterns and ground moisture fluctuations and cycles” which would have been completed in the six years since practical completion, and set out data from the Bureau of Meteorology (BOM) detailing the extreme weather that had been experienced in this period, concluding: “The periods of dry weather along with the periods of extremely wet weather experienced over the last 6 years as verified by the Bureau of Meteorology data, means that all expected soil swelling and shrinkage extremes that can be allowed for and are to be considered under AS 2870–2011 have already occurred”. On being taken to this evidence, Mr Camenzuli expressed the view, contrary to the opinion stated in his report, that there had in fact not been a single shrink and swell cycle in the past six years: “I don’t see how anyone can say ‘The cycles that we have experienced’ because we haven’t received one cycle of wetting and drying and wetting again”.

[62]  When Mr Camenzuli was asked whether he now said what was stated in his report was inaccurate, he responded as follows:

LE PLASTRIER: So you’d say that it’s not accurate to conclude that we’ve undergone a number of shrink and swell cycles over the last five years?

WITNESS CAMENZULI: Okay, now, when you talk about that, you have to talk about the order of magnitude that we’re talking about. Now, the code says 95% of expected movement; it dwells on that. Now, the issue is that from day to day you have some moisture change. Yesterday, it didn’t rain. Today, it rained. There’s a moisture change.

But those moisture changes are not significant to be, you know, to use as a basis for determining, as a professional, ‘look, okay, the house is experienced the loading that is expected.’ I mean, Australia has drought, seven year droughts; we just went through one a few, a decade ago or something. Don’t hold me to it. I don’t work for BOM. But a while ago, there was a seven year drought. Now, I consider that a dry period, right. Now, we’re going through the wettest period in a long time.

I think three years ago was a wet period. So, you know, a drought. You go through a wet period. If we go through another drought, I say we’ve accomplished one major cycle. I mean, but every, in every cycle, you have harmonics; you have little cycles based on a large, if someone can see my finger, little cycles all on a major cycle. I’m talking about the major cycles. People prefer to talk about day to day changes as a cycle. I don’t.

LE PLASTRIER: So I’ll just ask the question again. Do you say that it’s not accurate to conclude that we have undergone a number of shrink and swell cycles?

WITNESS CAMENZULI: If we talk about a day to day cycle, yes, we’ve achieved that. If we talk about major seasonal things, the data provided by BOM provides the order of accuracy of what we’re talking about. They gave yearly averages. So I’m talking about yearly cycles. Now, not yearly cycles, but yearly periods. That data provided two wet period — two dry periods, three, three wet periods, and a near normal period. If we look at that data, my assessment is we haven’t completed a cycle because we haven’t went through a period of dry, you know, dry.

[63]  It is difficult to identify from this response:

(1)  the basis on which Mr Camenzuli distinguishes between “little cycles” and “major cycles”, and his definition of each type of cycle;

(2)  the reason why Mr Camenzuli considers that, in the context of the shrinking and swelling of soil, it is appropriate to consider yearly or multi-year cycles, rather than seasonal cycles (particularly given the opinion which he previously expressed that there had been a number of cycles, which must have been based on seasonal cycles rather than yearly cycles, and the CSIRO publication quoted above in relation to “seasonal swelling”, which focuses on “rainy or dry periods, usually of weeks or months”); and

(3)  whether or not Mr Camenzuli’s opinions on these matters are based on specialised knowledge and, in particular, the extent to which Mr Camenzuli’s views on “cycles” and changes in moisture over time are based on his own observations of the weather, or BOM data, or a mixture of both.

[64]  Secondly, Mr Camenzuli had a tendency to use disparaging and dismissive language when responding to the opinions and reasoning of other experts. The use of such language detracted from, rather than strengthened, the opinions which Mr Camenzuli expressed. For example, he accused other experts of being “misleading”; of writing “fluff”; of behaving in a manner that was “very disappointing for an expert of his purported calibre”; of taking an approach which would be expected of “a novice … not a seasoned expert”; of being “non-sensical”; of being prone to “rant about irrelevant matters that obfuscate the underlying design flaws”; of being “unprofessional”; and of expressing views that are “blatantly incorrect, unfounded and embarrassing”. He even hinted at dishonesty, suggesting of one expert that it reflected “poorly on someone as experienced as [the expert] to err in such a simple task if it was unintentional” (emphasis added).

[65]  Mr Camenzuli was taken to a passage in one report where he had commented on the evidence of another expert, who had purported to express an opinion regarding a measurement based on a photograph. In that passage, Mr Camenzuli stated that to “claim to be able to determine the distance in the photograph is preposterous”, pointing to matters such as the “skew angle the picture was taken from” and “the distortion of the lens”. However, at a later point in the same report, Mr Camenzuli himself expressed a “strongly held view” regarding the measurement of a crack, which was based solely on a photograph, claiming that this involved “a well proven process”. He did not, in doing so, make any qualification about skew angles or lens distortion. It is difficult to see how a measurement based on a photograph is, when undertaken by another expert, “preposterous”, but when undertaken by Mr Camenzuli, a “well proven process” that can ground a “strongly held view”.

[66]  Thirdly, Mr Camenzuli referred in his evidence to other projects (often unspecified) in which he had encountered instances of defects in the work of Zanuttini and Metricon. He claimed to be aware of “a number of other cases currently going to Court” involving slabs engineered by Zanuttini, and of “many more jobs” where Metricon’s work was defective. For example, he claimed that he had “undertaken dozens of house inspections of Metricon homes” and had “found less than 10 to 15% of the roofs to be correctly secured”. It was not clear whether these matters were advanced to bolster his opinions, or matters which he took into account in forming his opinions, or were simply irrelevant asides.

[67]  I do not, however, accept Zanuttini’s submission that Mr Camenzuli is not a witness of credit. I formed the view that Mr Camenzuli sought to provide the Court with his honestly held opinions regarding the matters at issue in the proceedings, and sought to act as an expert assisting the Court on matters within his expertise rather than as an advocate. However, the manner in which he expressed his views, including his discursive answers and his tendency to dismiss opposing views, did make it difficult at times to determine the basis for his opinions and the basis on which he disagreed with the opinions expressed by the other experts.

[68]  Accordingly, I have taken Mr Camenzuli’s opinions into account when considering each of the defects in the slab as well as the consequences of those defects and have considered, when addressing those matters below, the substance of his opinions, the basis of those opinions and the weight to be afforded to those opinions in the light of the other expert and documentary evidence.

(emphasis added)

The link to the full report may be found here.