The judgment of Stephens J in McGovern -v- Sharkey  NIQB 117 contains some important observations in relation to the Bolam test and the role of evidence and experts in this context. It demonstrates that the credibility of a lay witness can be of considerable importance in the context of clinical negligence.*
The claimant was claiming in negligence against an Ophthalmic Surgeon in relation to treatment to his right eye.
 Disputes about questions of fact depend on the usual burden and standard of proof. However in relation to clinical or professional judgment the position is different. Bolam v Friern Hospital Management Committee  2 All ER 118 established that, in determining whether a defendant has fallen below the required standard of care, regard must be shown to responsible medical opinion, and to the fact that reasonable doctors may differ. A practitioner who acts in conformity with an accepted current practice is not negligent “merely because there is a body of opinion which would take a contrary view.” In Hunter v Hanley 1955 SLT 231 at 217 it was stated that
“In the realm of diagnosis and treatment there is ample scope for genuine difference of opinion and one man clearly is not negligent merely because his conclusion differs from that of other professional men … The true test for establishing negligence in diagnosis or treatment on the part of a doctor is whether he has been proved to be guilty of such failure as no doctor of ordinary skill would be guilty of if acting with ordinary care … “
That test in Hunter v Hanley, was approved in Maynard v West Midlands Regional Health Authority  1 All ER 635 and Lord Scarman also stated
“It is not enough to show that there is a body of competent professional opinion which considers that theirs was a wrong decision, if there also exists a body of professional opinion, equally competent, which supports the decision as reasonable in the circumstances. …
Differences of opinion and practice exist, and will always exist, in the medical as in other professions. There is seldom any one answer exclusive of all others to problems of professional judgment. A court may prefer one body of opinion to the other, but that is no basis for a conclusion of negligence.
… I have to say that a judge’s ‘preference’ for one body of distinguished professional opinion to another also professionally distinguished is not sufficient to establish negligence in a practitioner whose actions have received the seal of approval of those whose opinions, truthfully expressed, honestly held, were not preferred. If this was the real reason for the judge’s finding, he erred in law even though elsewhere in his judgment he stated the law correctly. For in the realm of diagnosis and treatment negligence is not established by preferring one respectable body of professional opinion to another. Failure to exercise the ordinary skill of a doctor (in the appropriate speciality, if he be a specialist) is necessary” (emphasis added).
 In Bolitho (Administratrix of the Estate of Patrick Nigel Bolitho (deceased)) v City and Hackney Health Authority  4 All ER 771 it was established that a doctor could be liable for negligence in respect of diagnosis and treatment despite a body of professional opinion sanctioning his conduct where it had not been demonstrated to the judge’s satisfaction that the body of opinion relied on was reasonable or responsible. In the vast majority of cases the fact that distinguished experts in the field were of a particular opinion would demonstrate the reasonableness of that opinion. However, in a rare case, if it could be demonstrated that the professional opinion was not capable of withstanding logical analysis, the judge would be entitled to hold that the body of opinion was not reasonable or responsible. Accordingly the final arbiter as to whether there has been professional negligence is the court and not the medical profession. It is for the court to decide whether the requisite logical basis for a defendant’s expert medical opinion is absent. The legal question is as to what features particularly characterise an expert medical opinion as one that is “illogical”, “irresponsible”, and “indefensible”. It is clear that merely being a minority view of accepted medical practice does not, of itself, render that view “illogical” or “irrational” in the Bolitho sense. However it is suggested that a court would be more ready to find that the body of opinion was not capable of withstanding logical analysis if there was a dubious expert whose professional views existed at the fringe of medical consciousness, see Khoo v. Gunapathy d/o Muniandy  2 S.L.R. 414, at . Another example would be “a residual adherence to out-of-date ideas” which “on examination do not really stand up to analysis” see Hucks v. Cole  4 Med. L.R. 393.
 It is however important to consider some limitations to the Bolitho test. A practice is illogical if there was a “clear precaution” which ought to have been, but was not taken. In this case the precaution that is suggested is that there ought to have been a diagnostic vitrectomy after one month given the risks of an unidentified tear of the retina and what is suggested was the lack of response to steroid treatment. However if there are risks attached to the precaution, in this case the risks associated with operating on an inflamed eye and the risk that the operation will not resolve the underlying problem, and one body of medical opinion considers that the risks ought to have been taken and the other does not then there is no “clear precaution” but rather a balancing of risks. In such circumstances both sets of expert opinion withstand logical analysis. For the plaintiff the expert opinion being that the risk of an adverse outcome, in that a tear was present in the retina, should have been prevented by taking the precaution of performing the vitrectomy. For the other body of expert opinion on behalf of the defendant, the precaution of performing a vitrectomy would have posed an unacceptable risk of operating upon an inflamed eye where given the diagnosis of ERD the operation would not have achieved a satisfactory outcome. This is merely a different weighing of risk rather than a determination that the defendant’s expert opinion is illogical. The precaution that is being suggested is not a “clear precaution” but rather a precaution which involves a balancing of risks and that is a matter of clinical judgment with a logical basis.
 Another feature of applying the Bolitho test is that it introduces a lack of symmetry as between the plaintiff and the defendant’s expert evidence. The defendant’s expert has only to persuade the court that his views are capable of withstanding logical analysis, but he does not have to satisfy the court that the views of the plaintiff’s expert are not capable of withstanding logical analysis. However, the plaintiff’s expert has to do both.
 If the case is one that involves clinical judgment to which the Bolam test applies, and if the medical practitioner does produce evidence that his practice was supported by a responsible body of medical opinion, then, in the words of Sedley L.J. in Adams v. Rhymney Valley DC  Lloyd’s Rep. P.N. 777, at ,
“the judge or jury have to accept the opinion of a body of responsible practitioners, unless it is unreasonable [in the Bolitho sense]” (emphasis added).
Accordingly in an action involving clinical judgment there is a two-step procedure to determine the question of alleged medical negligence:
(a) whether the medical practitioner acted in accordance with a practice accepted as proper for an ordinarily competent medical practitioner by a responsible body of medical opinion; and
(b) if “yes”, whether the practice survives Bolitho judicial scrutiny as being “responsible” or “logical”.
 Questions of fact and the question as to whether there was negligence are not to be conflated. Questions such as whether in the event there was a right retinal tear or hole in December 2006 or whether there was inflammation in the right eye in 2007 or whether there was scleral thickening in the right eye are questions of fact to be determined on the balance of probabilities with the onus of proof being on the plaintiff. The question of clinical and professional judgment as to whether a responsible body of medical opinion would form the view, in say January 2007, that there was a right retinal tear or hole or that there was inflammation in the right eye or that there was scleral thickening in the right eye are all subject to theBolam test as qualified in Bolitho. In some cases the determination of a question of fact may lead inexorably to a finding that the medical practitioner did not act in conformity with an accepted current practice. In others it may have no such impact. So for instance in this case if there was a factual finding, on the balance of probabilities, that on 26 December 2006 the first defendant was informed that the plaintiff had suffered a sudden and profound loss of vision in his right eye and that the plaintiff’s right eye was not assessed or if the plaintiff was not advised to have his right eye assessed that day then inexorably that would lead to a finding that the first defendant had not acted in conformity with an accepted practice. Inexorably because no logical accepted current practice would do or advise anything other than immediate action. However if the factual finding was that the first defendant was informed that the plaintiff had some extremely modest effect on his vision in conjunction with a history that drops had not been taken then (though there was a dispute about this) it might be that to delay an examination until 4 January 2007 and to recommend that the plaintiff use his drops was in conformity with a logical accepted current practice.
ASSESSMENT OF THE EVIDENCE
 In assessing credibility I seek to apply the principles set out by Gillen J in Thornton v NIHE  NIQB 4 where he stated
“ Credibility of a witness embraces not only the concept of his truthfulness i.e. whether the evidence of the witness is to be believed but also the objective reliability of the witness i.e. his ability to observe or remember facts and events about which the witness is giving evidence.
 In assessing credibility the court must pay attention to a number of factors which, inter alia, include the following;
• The inherent probability or improbability of representations of fact,
• The presence of independent evidence tending to corroborate or undermine any given statement of fact,
• The presence of contemporaneous records,
• The demeanour of witnesses e.g. does he equivocate in cross examination,
• The frailty of the population at large in accurately recollecting and describing events in the distant past,
• Does the witness take refuge in wild speculation or uncorroborated allegations of fabrication,
• Does the witness have a motive for misleading the court,
• Weigh up one witness against another.”
 I have arrived at a number of factual conclusions adverse to the plaintiff based on my assessment of his presentation, on the fact that he deliberately failed to disclose his eye condition to his road traffic insurers and to the licensing authorities choosing instead to continue to drive when he knew that he represented a significant danger to other road users. I also consider that his recollection of events which occurred some 7 years ago was faulty.
 In relation to the plaintiff driving at a time when he knew that he ought not to be the evidence was that on 14 July 2008, that is after a series of operations involving both of his eyes, he purchased a two year old Volkswagen Passat four door salon motor vehicle. At that time the visual acuity in his right eye was totally inadequate to drive but the visual acuity in his left eye had improved to 6/12 by February 2008 and remained at that level throughout 2008. By February 2009 his left visual acuity had deteriorated to such an extent that he fell below the standard for driving and on 9 June 2009 Mr Ezra told the plaintiff that he should not be driving. The plaintiff agreed with Mr Ezra to adhere to that prohibition. In addition Mr Ezra wrote to the plaintiff’s general practitioner and to the plaintiff’s optometrist to inform them that the plaintiff should not be driving. Accordingly 11 months after the plaintiff purchased his motor vehicle he knew that he should not be driving. However he did not sell his motor vehicle until May 2014 some five years later. Also he did not cancel his motor vehicle insurance policy until 27 June 2014. At the date that he disposed of his motor vehicle its recorded mileage was 52,000. In his evidence the plaintiff stated, without producing any corroborative evidence, that when he purchased it that it had a very high mileage, which he estimated at 50,000.
 During that period he completed proposal forms for insurance declaring use of the motor vehicle for both business and social purposes with an estimated annual mileage of 14,000. He positively denied on one insurance proposal form that he had defective vision not corrected by glasses despite a reminder of his legal obligation to inform the driver’s medical branch of the DVLA if he had any disability that affects or may become likely to affect his fitness as a driver. On 19 May 2012 whilst driving his car he hit the entrance gate to his sister’s house in the Balmoral area of Belfast causing damage costing £1,500 to repair. He mislaid his driving licence on two occasions and as a consequence he applied for a replacement licence. The first was on 24 October 2007 and the second in 2010. He lied to the licensing authorities on both of those forms in response to questions as to disability.
 On 2 December 2012 the plaintiff was seen by Mr McHugh MD, FRCS, FRCOphth DO, Consultant Ophthalmic Surgeon, who took a history from the plaintiff that “he can drive but has to exercise great care because of his reduced vision. He never drives at night.”
 In an amended statement of claim stated to be served on an unspecified date in December 2013 but in fact served on 11 April 2014 the plaintiff alleged in the particulars of personal injury that “he does not drive at night”. In his further amended statement of claim served 1 July 2014 the particulars of personal injury include an allegation that he “no longer drives”. The plaintiff stated in evidence that as from November 2013 he stopped driving and that he kept his car so that his wife from whom he is separated and who has a car of her own could drive his car.
 In his evidence the plaintiff acknowledged that he lied to his insurance company and to the licensing authorities about his disability. He acknowledged that he had been in breach of the agreement with Mr Ezra that he should not drive. He stated that he only drove a short distance to church early on a Sunday morning and to a local shop again at a time of the day when there was little traffic. In relation to other journeys he asserted that he used taxis. I consider that quite irrespective of what he had been told by Mr Ezra it was quite obvious to him that he should not drive. He was prioritising his own needs. He lied consistently. He chose to imperil the lives of others. I consider that his evidence in court that he kept his car for the convenience of his wife from whom he was separated and who had her own car was also inaccurate to his knowledge. I consider that he drove to a greater extent than he was prepared to admit in his evidence and that he was not being candid.
 In broad terms I accept the evidence of Mr Sharkey. He presented in court as a dedicated, concerned, highly qualified and extremely experienced professional. Once he saw the plaintiff on 4 January 2007 he responded by seeing the plaintiff on a frequent and repetitive basis at the Ulster Independent Clinic without any fee being charged. This was in ease of the plaintiff who would otherwise have had to travel to the RVH and also to ensure that there was continuity of care. As is apparent I consider that in relation to some aspects of the first defendant’s care of the plaintiff it fell below an acceptable standard in the Bolam and Bolitho sense. Accordingly there is the potential for an inference that if the first defendant reacted inappropriately on those occasions, that he did so on other occasions. I reject any such inference having seen and heard the first defendant. Also I consider that his recollection of events was far more likely to be correct than that of the plaintiff. I come to that conclusion not only on the basis of the manner in which he gave his evidence but also on the basis that he had the advantage of being able to rely on the notes and records and also on his usual practice. There were numerous conflicts of evidence between the plaintiff and the first defendant and I do not intend to rehearse all of them but in general in order to resolve such conflicts in favour of the plaintiff I have looked for some degree of inherent probability or some degree of support in the medical notes and records. I give as an example one instance of a conflict of evidence between the plaintiff and the first defendant which relates to the plaintiff’s assertion that on 29 March 2007 he requested the first defendant to arrange for a second opinion. The first defendant denied that any such request was made and also stated that if a second opinion had been requested he would have agreed. Having seen both the plaintiff and the first defendant give evidence and accepting as I do that there was no reason why the first defendant would not obtain a second opinion and also finding no support for such a contention outside of the plaintiff’s evidence, I reject the plaintiff’s evidence in relation to that allegation and prefer the evidence of the first defendant.
WHICH EXPERT THE JUDGE PREFERRED
The case is also interesting because the judge gave reasons for preferring one expert over another.
 Mr Aylward FRCS FRCOphth, MD, Consultant Vitreoretinal Surgeon at Moorfields Eye Hospital, was called on behalf of the first defendant to give expert evidence as to a responsible body of medical opinion. I accept that he represented a responsible body of medical opinion and that his opinions were both “truthfully expressed” and “honestly held.” It is not necessary for the determination of this action to decide whether I preferred his evidence to the evidence of Mr McHugh, as in the realm of diagnosis and treatment negligence is not established by preferring one respectable body of a professional opinion to another. However if the question of preference had arisen then I would have preferred the evidence of Mr Aylward for all of the reasons set out by Ms O’Rourke in her closing submissions including the external support for Mr Aylward’s opinions in the literature, his personal experience of cases of ERD and the detail of his evidence, for instance, in relation to the measurement of scleral thickening with calipers, which evidence was subsequently and independently supported by the world expert in that field, Marie Restori.
 Mr McHugh, MD, FRCS, FRCOphth DO, Consultant Ophthalmic Surgeon, was called on behalf of the plaintiff to give expert evidence as to a responsible body of medical opinion. I consider that there was little, if any, support for his views in the medical literature. It was not put to him in cross examination that he did not represent a responsible body of medical opinion and in that circumstance I will proceed without deciding on the basis that his views represent a responsible body of medical opinion albeit a minority view.
 Marie Restori, Consultant Physicist at Moorefields Eye Hospital, gave evidence in relation to the ultrasound scans. She is an international and internationally recognised expert in the use of ultrasound in ophthalmic diagnosis and measurement with over 30 years’ experience in this field. In short she is a pre-eminent world class expert. I accept her evidence.
 Mr Ezra FRCOphth, FRCS (Glasgow), BEVRS, RSM, AAO Consultant Vitreoretinal Surgeon, Moorfields Eye Hospital and St George’s Hospital, London, Honorary Consultant Vitreoretinal Surgeon Great Ormond Street Hospital gave evidence including his opinion as to whether the tears seen at operation on 3 September 2007 were long standing or caused in the operation. His evidence was arranged at short notice and understandably he had not considered the medical notes and records in detail. Despite being the operating surgeon and given that he had not considered the medical notes and records in detail I do not consider that he was in any better position than Mr Aylward to give evidence on the issue as to when the tears or holes occurred. Rather I prefer the evidence of Mr Aylward who had exhaustively analysed all the medical notes and records.
The claim was dismissed.
 I have found as a fact that the first defendant was not specifically asked by the plaintiff in March 2007 to arrange a second opinion. It is alleged that the first defendant fell below an acceptable standard of care in that of his own volition he did not request a second opinion and specifically an opinion from an expert in inflammatory conditions of the eye. The first defendant did not consider it necessary to seek a second opinion given the clear clinical signs of an ERD, his own level of expertise in that he had been trained in inflammatory eye conditions and that there was no dedicated inflammatory eye specialist in Northern Ireland. Mr Aylward’s evidence is that this was in accordance with a practice accepted as proper for an ordinarily competent medical practitioner by a responsible body of medical opinion. I accept that evidence. I consider that this practice survives theBolitho judicial scrutiny as being “responsible” or “logical” in that the diagnosis was of an ERD there being clear clinical signs and the standard treatment was being followed. If I am incorrect in that finding I consider that the plaintiff has not established that any different treatment would have been commenced if an inflammatory eye specialist had been consulted.
 Mr Aylward represents a respectable body of medical opinion. His evidence was that at the time and even with the benefit of hindsight the correct diagnosis in the period January-June 2007 was of an ERD and that the correct treatment was that used by the first defendant. Mr Aylward was of the opinion that the combination of symptoms makes the diagnosis of ERD not only reasonable but overwhelmingly likely. Indeed, he goes further and states that he would not have advised an operation for a further month. In essence he arrives at the diagnosis of an ERD on the same basis as the first defendant. Accordingly I hold that the first defendant acted in accordance with a practice accepted as proper for an ordinarily competent medical practitioner by a responsible body of medical opinion.
 I also consider that the practice survives Bolitho scrutiny as being “responsible” or “logical”. To operate on an ERD does not address the cause of the generation of fluid and carries substantial risks.
 Those findings are sufficient to determine this case in favour of the defendants. However, I also find that the plaintiff has not established that the retinal holes found at operation on 3 September 2007 were in fact present any earlier than 17 May 2007 when the intra ocular injection was performed. I consider that the most likely cause of the retinal holes was pulling of the vitreous on the retina prompted by the intra ocular procedure and indeed potentially also by the operation which was performed on 3 September 2007. This is consistent with the symptoms of an ERD at an earlier stage and supported by the evidence as to the mechanics by which an iatrogenic tear or hole can be formed.
 The factual conclusion that no hole or tear was present until at the earliest May 2007 means that if an operation had been performed, as suggested by Mr McHugh in February 2007, then no hole or tear would have been found at that operation. Accordingly, if there was any failure to operate in February 2007 it did not cause any adverse impact on the plaintiff’s condition. Indeed, I accept that operating in February 2007 may well have led to a worse outcome for the plaintiff.
 I find for both defendants in relation to the issue of liability and dismiss the plaintiff’s claim.
* I appreciate that this is a Northern Ireland judgment. However the law as to clinical negligence, and the principles in relation to the assessment of witnesses, are of general relevance.
ALSO ON THE ISSUE OF EVIDENCE IN CLINICAL NEGLIGENCE CASES
ON WITNESS CREDIBILITY