In a recent English decision noted by Gordon Exall, Thefaut v Johnston  EWHC 497 (QB), the trial judge spoke of the cross examination of an expert witness on upon the basisthat he had failed in his report to record his prior knowledge of the defendant as a colleague on various professional bodies and his regard for the defendant as a surgeon of repute and skill.
At  the trial judge said:
…In the specialist field in issue there are a relatively small number of surgeons. They tend to know, or know of, each other, especially if they have been in practice for many years and have had prior involvement with each other as colleagues serving in the various specialist professional bodies. In such circumstances there is a high probability that when one of this select group is instructed to act as an expert in a case he or she may know of the Defendant either personally or by repute. This was the case of Mr Gullan in relation to Mr Johnston. He knew him both from co-participating in professional bodies and by repute. This did not in my judgment necessarily mean that he could not give expert evidence in the case. He was not so close to Mr Johnston that, objectively speaking, his independence was compromised. But it is my view that Mr Gullan would have been far better to get out in the open his personal knowledge of Mr Johnston. A concise but accurate and comprehensive paragraph in his report setting out the bare facts of his knowledge of Mr Johnston would have sufficed. This would have taken much of the sting out of the cross examination which did, I am bound to say, leave Mr Gullan feeling and sounding defensive. The issue here is the appearance of bias. The inevitable questions in cross examination which followed from the omission were along the lines that Mr Gullan was advancing a view which was tailored to support a fellow professional who was in a predicament, and hence lacked objectivity. If this had in fact been Mr Gullan’s intent and object when giving evidence it would have struck at the very heart of his professionalism and objectivity and it could have rendered his evidence inadmissible: see, e.g. EXP v Dr Charles Simon Baker  EWCA Civ 63 at paragraph  per Irwin LJ. As I have observed I do not accept that Mr Gullan gave his evidence other than objectively and independently.