There is more to being a good medico-legal expert than being a good doctor. It is rare to win a clinical negligence case (and this is my field) without good experts. But sometimes, cases go wrong because the expert lets a client down.
With the right expert evidence, people who should get damages win their cases but those who should not do not pursue claims (and hopefully understand why). Costs are incurred on the right cases. My goal is for the right people to get damages and for the health service to spend the minimum on costs in the process.
So after many years of running clinical negligence claims, here are five top tips on how to be a good medical expert.
Many years ago, an expert reported for me that a surgeon caused harm because he used the wrong technique in carrying out an unusual procedure (a Lue procedure for Peyronie's Disease). The claim was strongly defended. My expert produced weighty reports and explained his view convincingly in the conference with counsel. But at a late stage, when the pressure was on, he confessed that he had never actually carried out the procedure. The expert thought he knew how to do it – but he was wrong. He led my client wrongly to believe he had a good claim. The result was not just disappointment but a lot of wasted money. I should never have instructed him and he should never have accepted the instructions. I learned a lesson and now always check an expert's experience.
Judges, being wiser than I was then, will probably look carefully at an expert's CV at trial. See, for instance, how Mr Justice Foskett, in a 2011 case, worked his way through an impressive CV and commented that she was "eminently well qualified to offer an opinion on relevant issues in this case" .
Don't allow yourself to be trumped by someone who knows more than you do. If you are not the right expert, don't put yourself forward.
But it is not always the most impressive CV that impresses the judge. Sometimes the Court will prefer a less experienced expert if they spend more time at the coal face. In one case, the Court preferred the evidence of two less experienced experts (although, to be fair, they were still both professors). As the judge said, "…they had the advantage of being more in the front line of medical practice and did not spend an undue amount of time in medico-legal work"  – which suggests a degree of suspicion of the 'professional expert'.
There are occasions when an expert is too specialist. Suppose the Court is judging the standard of knee surgery by a general orthopaedic surgeon in a district hospital. In this case, it is unlikely to want to hear from a specialist knee surgeon in a tertiary referral centre. There may be a suspicion that the specialist's standards are too high.
The Civil Procedure Rules require an expert to be impartial. Your overriding duty is to the Court. It may sound naïve to think that an expert will be totally impartial, and it probably is. But that should be the aim. We all know of 'claimant experts' and 'defendant experts'. I do not want to instruct either. I want experts who give an honest and impartial view – not ones who tell me what I want to hear or undermine a legitimate claim. Experts who display obvious bias will undermine their own evidence.
In plenty of cases, biased experts have been recognised for what they are.
Consider a recent commercial case where the judge said this about the defendant's expert:
"I formed the impression that he has…developed what might be regarded as an expertise in giving evidence. [He] was extremely careful in giving answers. I increasingly took the view that this was because his first priority was to avoid saying anything that might damage [the defendant's] case" .
Ouch. Needless to say, the judge was persuaded by the claimant's expert who "gave clear and direct answers".
In another very recent case, the judge said of one expert:
"I have to say that I found [his] evidence to be absurd…Had he made proper enquiries of his client…he would have been in a much-informed position. But he did not do so."
Comments like this from a judge are likely to form an epitaph to a forensic career.
One medical expert I instructed used to take over conferences with counsel with advice on the law and likely award at trial. Some have even re-qualified in law. In one recent case, although the judge accepted the expert's evidence, he expressed concern that the (otherwise excellent) expert used words like 'submit' and referred to his 'argument' .
I do not think this expert is anything other than highly professional and independent in his evidence. But the choice of his language was unfortunate. So avoid the temptation to plead a case. Stick to giving evidence.
What do you do when there is a conflict of evidence? The answer is that you give opinions based on both scenarios. You leave deciding which is correct to the judge. You do not base your view only on what the party who instructs you says.
If you do not follow this advice, you risk:
It is a constant frustration to be served with expert reports from experts who assume that their client's account of the facts is correct and do not engage with the other possibility.
It is much better to consider your evidence carefully and carry out research before you set pen to paper (or finger to keyboard). There is nothing more annoying than a case collapsing at a late stage when an expert is forced into a change of view. I would not encourage experts to stick with a view in the face of clear evidence that they are wrong. The expert whose evidence was criticised as 'absurd' was also criticised for failing to make reasonable concessions. In the judge's words, "His evidence on a number of points was unsatisfactory and showed an unwillingness to concede anything" . But it is better to do your homework and get it right the first time.
I am unlikely to instruct an expert again once they have let me down.
 The expert was Professor Kirkham. "Her CV demonstrates that she is a highly qualified and highly distinguished paediatric neurologist who has been a Consultant for about 20 years with clinical experience at Great Ormond Street Hospital and Southampton General Hospital. She was a senior lecturer in Paediatric Neurology at the Institute of Child Health for approximately 16 years prior to her appointment as Professor of Paediatric Neurology at the Institute in October 2006. Her written contribution to medical literature, both in textbook form and article form, is very extensive and her particular research interest has been in the detection and prevention of brain damage in acutely sick children. Her recent Doctor of Medicine thesis at the University of Cambridge was entitled 'Cerebral Haemodynamics in Normal Subjects and Children in Coma'. She was eminently well-qualified to offer an opinion on relevant issues in this case." Morwenna Ganz v Dr Amanda Jillian Childs and others,  EWHC 13 (QB).
 Melhuish v Mid Glamorgan Health Authority  MLC 145
 Edward Lifesciences v Boston Scientific  EWHC 755 (Pat)
 BHL v Leumi ALB Limited [20170 EHWC 1871 (QB)
 Muller v Kings College Healthcare Foundation Trust  EWHC 128 (QB)
 BHL v Leumi ALB Limited  EHWC 1871 (QB).
Can you spot the three medico-legal errors in what follows?
"His care was substandard (a responsible body would not have done the same) and breached his duty."
I have seen countless variations of that sentence. It does not satisfy the legal test of breach of duty and will irritate the judge.
First, 'substandard' is meaningless from a legal point of view. The test of breach of duty is whether a doctor has acted in accordance with a practice rightly accepted as proper by a responsible body skilled in that particular art. So what we need to know is not whether the treatment was the gold standard, bog-standard or substandard but whether there is a responsible body who would (with good reason) have done the same.
Secondly, experts sometimes turn the Bolam test upside down and say that a responsible body would not have done the same. But the test is whether there is a responsible body who would have done the same. That is quite a different thing.
Finally – and at the risk of pedantry – it is not for the expert to say whether there was a breach of duty. It is for the expert to define the standard of care and then leave the judge to draw the conclusion as to whether there was a breach of duty. Saying that care failed to meet the Bolam test implies a breach of duty. So if the judge accepts that evidence, a finding of breach of duty is not a great leap of logic. But it is still the judge's leap and not yours.
Establishing liability, of course, entails not just a breach of duty but causation. In most cases, the test is whether outcome X would have happened 'but for' the breach of duty. (There are other causation tests applicable to other situations but I cannot cover them here – and the 'but for' test covers the vast majority of cases.)
In relation to past events, all we need here is to establish what would 'probably' have happened. On the balance of probabilities, a 51% likelihood of survival may lead to an award of damages; whereas 50% leaves her with nothing. Simple probabilities are what we need, even if they seem a rather blunt instrument. This may not seem very sophisticated to the medical mind. But it is as simple as that. It may be a matter of life and death – whether the claimant would have survived but for the breach of duty. So please avoid telling us too much about what possibly would have happened – past possibilities do not take us anywhere. And please avoid, if possible, saying that the outcome was 50/50 (unless it really was exactly 50/50). Better to come off the fence and say 49/51 or 51/49. This makes all the difference.
When it comes to future events – what might or might not happen – different principles apply. Here quantifying possibilities are important. If, for instance, there is a risk of amputation, we need to know the degree of risk – say 30% or 60%. The claimant may need to claim 30% or 60% of the loss arising in the event of amputation. So without a figure, we do not know the percentage to claim.
The rule is:
The best reports cite literature. Persuasive opinion rests on evidence. Without support, the judge has little to go on in determining whose evidence to accept. So, where possible, cite literature and show its relevance to the issues. You should undertake database searches and cite peer-reviewed literature, refer to international, national or local guidelines, or, in establishing current practice, textbooks. Make sure that the textbooks are up to date.
Beware of attracting the sort of criticism a judge made of an expert in one case:
"Although there was a good deal of literature on the subject…Mr M did not rely on any of that…He only referred to it to dismiss the literature altogether…Instead he sought to rely on his own experience which, because it was both contradictory and undocumented, could not be the subject of meaningful research or comment by the defendant's experts." 
Or consider this comment by another judge:
"Mr C's valuation approach effectively involved putting the available information into a black box from which a figure emerged based entirely on his gut feel. The problem with a valuation being pronounced ex cathedra in this way is that it is not capable of being tested or subjected to any rational scrutiny. It amounts to saying, 'Trust me, I am an expert valuer…' Experts' opinions, if they are to be accorded any weight, need to be supported by a transparent process of reasoning." 
At the risk of undermining the last tip, on occasion, there simply is no research or textbook evidence to cover the point. Rather than say, "I don't know", you should give a view if you can. After all, the Court needs to make a finding one way or the other. It is looking to you for assistance.
You can base your view on your own clinical experience. Give your reasoning. Say that you know of no research on the point but you are doing your best to give an answer despite an absence of data to support it. Doing so does not align you with Mr M above – who simply dismissed the literature. Nor does it amount to Mr C's ex cathedra pronouncements. You are simply doing your best to assist the Court in addressing an issue on which it needs evidence.
My final tip is to be thorough and careful at every stage of the claim. Prepare for conferences and particularly for experts' meetings as if you were preparing for trial. Take care when responding to questions from the other side. Careless talk costs cases. An ill-thought-out response to a question can undermine several years of work. Once a comment has been made in writing, it is very difficult to backtrack. Even if you explain later that it was not really your view, no one will be persuaded and you can expect some tough cross-examining at trial.
The most frustrating experiences I have had with experts have been when the joint statement of experts arrives and an ill-prepared expert has lost sight of the issues and strayed from a carefully considered opinion. Explaining to a client why their case, which had looked so promising over the past three years, is unlikely to succeed is not a pleasant experience for the lawyer. It is devastating for the client. Sometimes we have to do it because that is simply how the evidence turns out. But we should not have to do it because an expert is not well prepared.
Working with experts who think things through carefully from the outset, understand the legal tests, support their views with evidence, listen to reasonable points but are consistent from beginning to end is a pleasure. They make the legal system work as it should. These experts provide the specialist opinion the Courts need to decide difficult cases. They enable people who should be compensated to obtain damages. And they protect our health service from incurring costs where they should not. I hope that these tips help you to be that sort of expert.
 Nasir Hussein v Bradford Teaching Hospitals NHS Foundation Trust 2011
 Hirtenstein and another v Hill Dickinson LLP 2014