Attack on expert's credibility rejected

We have often drawn attention to cases in which claims regarding experts’ unreliability were supported. 

However in this case, the judge rejected the defendant’s submission which seriously attacked the expert’s credibility, claiming they were an unsatisfactory expert witness, more inclined to argue their clients’ case than to assist the court, and that the expert was not a witness on whose evidence the court could safely rely. They said that the expert’s evidence was shown in cross-examination to be unsupported, speculative and in many cases positively misleading.

The judge, however, did not accept that the expert was an unreliable witness. "On the contrary, and as will be apparent from my detailed discussion of her evidence below, I consider that she was impressive, and indeed more impressive than x."

The key paragraphs from the judgment are 224-237:

224. Dr Anna Bennett was trained as a conservator and holds a first class BSc degree in Archaeological Conservation and Materials Science from the Institute of Archaeology, University of London. She then held a one-year fellowship at the J. Paul Getty Museum California. She was awarded her PhD in 1988 from University College London, and a post-Doctoral Research Fellowship at the University of London in 1988 – 1990. She is a principal of Conservation and Technical Services Ltd (referred to at the trial as “CTS”), a company which she founded in 1989 and which is affiliated with the Centre for the Scientific Investigation of Works of Art. She has undertaken a wide variety of conservation and analytical projects over the years, providing conservation and analytical services to numerous well-known museums and institutions such as the National Trust. It is not necessary to set out the details of the work that she has done, or her fairly extensive recent bibliography. There was no dispute that she was an experienced and very well-qualified materials scientist, who has been working in conservation and analysis for over 30 years.

225. I saw her cross-examined over a number of days. At the time, I formed the view that she was an impressive witness who was seeking to assist the court. By and large, she gave short and direct answers to the questions raised, often agreeing with the proposition that was being put. On occasions, her answers were lengthy, but they were still (generally) directed to the question which had been asked, and the length of her answers usually reflected either the nature of the question and/or the fact that she was seeking to explain scientific concepts which were not straightforward to a judge without a background in materials science. Her evidence was clearly expressed and usually well-explained.

226. The Defendants submitted in closing that she was an unsatisfactory expert witness, more inclined to argue her clients’ case than to assist the court, and that she was not a witness on whose evidence the court can safely rely. They said that her evidence was shown in cross-examination to be unsupported, speculative and in many cases positively misleading. She was driven to admit, reluctantly, that assertions in her court report had no evidence to support them, and that she did the same in reports which had been prepared prior to the proceedings. She abandoned arguments without identifying the fact that she had done so, and without admitting that they were false arguments. She advanced entirely novel and unsupported explanations. Her evidence was constantly shifting. Overall, no part of her evidence on inauthenticity could be relied upon. The Defendants supported these submissions by reference to 7 particular points drawn from the evidence that she had given at various stages.

227. I have considered each of the points raised, and I do not accept this submission. My reasons as expressed in the following paragraphs address certain technical issues relating to the objects themselves, and therefore need to be read in conjunction with my discussion of the materials science in later sections of this judgment.

228. It is right to say that Dr Bennett, on some occasions, accepted that what she had said in her report was incorrect or too emphatic. An example, given much prominence in the Defendants’ closing, concerned her acceptance in cross-examination that some chlorine was present in the deposit which had been applied to the Frieze. As it seemed to me, this was to her credit: where a good point was made, she was willing to acknowledge it.

229. Moreover, I did not see that this point, about chlorine in the deposit, materially affected her evidence as a whole as to the authenticity of the Frieze. She had some much more fundamental and significant points concerning inauthenticity, including those relating to the absence of weathering, and modern tool marks. These are discussed in Section I below. Whether or not chlorine was present in the deposit was not in any way crucial to her conclusion. Indeed, she had made it clear almost at the start of her cross examination that definitive conclusions could not be drawn from deposits:

“Well, you have to be very careful when you look at deposits because deposits can have occurred, you know, after … a genuine object was overcleaned or something. So, you know, an applied deposit is -- you note it, but it may not be the most paramount for the authenticity of an object, because the actual weathering of the object itself, that’s the most important in terms of authenticity”

230. This passage, in my view, is evidence from an expert who is indeed seeking to assist the court, by warning against drawing a conclusion simply from a deposit, and being careful not to overstate things. As she said, an artificial deposit applied to the surface of an object is “part of the story of the object”. It was apparent throughout her evidence that, as she said in that quoted passage, the actual weathering of the object was the most important point. The Defendants’ various criticisms of her evidence in their closing did not, as it seemed to me, focus on her evidence as to the lack of weathering. Indeed, in relation to all of the objects apart from the Hari Hara, it was essentially common ground that there was an absence of any significant evidence of weathering.

231. A related criticism of Dr Bennett was that she made points in her pre-action reports, but these points were not then made in what was referred to as her “court” report, and that she did not draw attention to the fact that she was no longer making that point. I do not think, however, that an expert is to be criticised for omitting, from a report prepared in accordance with CPR Part 35, points which she no longer considers to be important, or that she may have reflected upon and decided were not good points. To my mind, that is what an expert should do. Nor do I think that an expert is required to draw specific attention to points which are no longer pursued. Those points will be apparent to the other party, which can if necessary ask questions about them.

232. Mr Green submitted that, in relation to answers made in her lengthy cross-examination, Dr Bennett sometimes made points which had not been made in her previous reports or in her court report. When a witness is under cross-examination for the best part of 2 days, and is dealing with a large number of questions of which she has not received advance notice, it is almost inevitable that responsive answers may include information or statements which have not, in exactly that form, been contained in earlier reports. A trial, and in particular cross-examination, has a considerable element of fluidity, with particular points becoming the focus of attention and being explored and responded to. In the present case, I did not think that any of Dr Bennett’s answers relied upon in this context (for example, her evidence as to feldspars in the context of the Hari Hara) represented a significant departure from points which she had previously made.

233. A point on which great emphasis was placed concerned statements by Dr Bennett which were made in relation to the existence of ceramic particles in the Krodha. As with most if not all of the points made by the Defendants as part of their attack on Dr Bennett, this is a long way from being a central point on the issue of whether the Krodha is or is not authentic. Indeed, it is not a point of any importance at all, and the existence or otherwise of ceramic particles was not relied upon by Dr Bennett in her court report or in her evidence in the witness box. Her conclusion in her court report is that the work contains modern particles, such as modern brass, nickel chrome steel with a vanadium hardener, gold dust, and pure molybdenum. There is no mention of ceramic particles. It is clear from that report that ceramic particles played no part in her analysis. Moreover, it was ultimately common ground that there is indeed substantial evidence of modern materials in the Krodha. Dr Nicola in his oral evidence said that he was sure it was not 100% an original object, although he could not know exactly the number of percent that the object was original: it could in his view be 80 per cent original, or 50% or 30%. He described the object as being subject to a few deep restoration interventions, and he agreed that it was possible to see plastic protruding from the cheek of the object. It followed from these answers, and indeed Dr Nicola’s overall conclusion, that it was possible that the object was 0% original.

234. Nevertheless, there was extensive cross-examination of Dr Bennett on the issue of ceramic particles in the context of statements which she had made in the second CRS pre-action report that she had written, and also some correspondence (exhibited to her court report) with Oxford Authentication. It was suggested to her that she had made knowingly false statements in that pre-action report and/or in the correspondence. She was, I think, completely baffled by the suggestion and denied it emphatically. I consider that she dealt well with this line of questions, and I do not think that there is any substance in the suggestion that, in relation to ceramic particles or otherwise, she made deliberately false statements intending to deceive. Nor is there anything which leads me to conclude that I cannot rely on her evidence. In order to explain why this is so, it is necessary for me to give some explanation of the history of how the question of ceramic particles arose, and to refer to Dr Bennett’s evidence about what she had written. However, the evidence on this issue is best explained and understood in the context of the more detailed discussion of the Krodha, and it is therefore contained in Section K below.

235. Dr Bennett’s conclusions on various issues were criticised on the basis that they were “merely speculative opinion”. Reference was made to her evidence that a deposit had been applied to simulate a burial sediment. In my view, however, Dr Bennett was fully entitled and qualified to offer an opinion as to the likely reason for a relevant feature of an object. When one is dealing, as here, with allegedly fake objects, there will be no direct evidence, from someone who saw what happened, of the precise steps that the forger took. However, just as a pathologist may be able to draw conclusions from the state of a body at a post mortem examination, a qualified materials scientist may be able to draw conclusions from an object as to what is likely to have happened. Whether or not I accept that evidence, and Dr Bennett’s conclusions, is a different question. But her evidence cannot be disregarded because she sought to infer what is likely to have happened.

236. Mr Green also submitted that I should take into account the possibility of “confirmation bias”. His point was that Dr Bennett had previously written pre-action reports which concluded that the pieces were inauthentic. She was therefore likely to reach the same conclusion in her court report. I can certainly see that an expert who has previously expressed firm views in an earlier report may well adhere to those views in a later report. I do not see anything wrong with this, provided that the expert is willing to consider new information and points which are made. In that regard, I have already noted Dr Bennett’s willingness to acknowledge good points that were made to her in cross-examination, and good points made by Dr Nicola. I also bear in mind that if the expert had expressed very different views in an earlier report, the opposite point would be made, namely that the expert has been inconsistent. I can see the possible danger of confirmation bias, with an expert rationalising points so as to accord with a previously held view. Whether or not this happened seems to me to depend upon my evaluation of the evidence of Dr Bennett on the particular pieces. This is addressed in the sections below.

237. Accordingly, I do not accept that Dr Bennett is an unreliable witness. On the contrary, and as will be apparent from my detailed discussion of her evidence below, I consider that she was impressive, and indeed more impressive than Dr Nicola. I certainly have more confidence in her views than the contrary views expressed by Dr Nicola.