26th July 2024
Often the criminal cases that feature prominently in the news are really not interesting from a legal(istic) perspective.
One could quite happily commentate on interesting legal issues and never engage with a case which has been on the front pages.
And one could follow ‘true crime’ stories and never come across an interesting legal issue.
There is usually not much of an overlap: ‘true crime’ and earnest, plodding legal commentary normally do not have that much in common.
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The Lucy Letby case has been prominent in the news now for some time.
She has been convicted of multiple murders and attempted murders.
But is there anything in her case which is of wider interest – or of concern – in respect of the legal system?
Is there an issue here about the process of criminal justice?
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Some people maintain she must be innocent; and some people insist she must be guilty; and there are many websites and social media posts setting out both of these positions.
This blogpost is not one of them.
I do not know if she is guilty or innocent. That is a matter for a jury – or an appeal court.
She may be a serial killer, or she may be a victim of a miscarriage of justice; that is for others to decide.
But there is, I think, an issue here of potential wider concern.
This may be a rare example of a front page ‘true crime’ story which also raises an important issue about the legal system.
And that issue is about the role of prosecution expert evidence in an adversarial criminal trial when the defence elects not to put in their own expert evidence (for good reason or bad).
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Lucy Letby was convicted, in part, on the basis of expert evidence.
The case against her was not entirely based on expert evidence; there was other evidence put before the jury.
But, on any view, it was an expert evidence heavy prosecution.
And that is not unusual – or wrong: there are many criminal prosecutions which depend on expert evidence.
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In our adversarial system, what often happens in a jury trial when there is reliance by the prosecution on expert evidence is that there is also expert evidence put forward by the defence.
In principle, the expert owes their duty to the court – and not to the party who has instructed him or her.
In practice, of course, the prosecution will put forward expert evidence that supports their case, and the defence puts forward expert evidence which supports their case; the experts are then examined and cross-examined by lawyers; the judge sums up; and the jury then weighs the evidence of the experts in its deliberations.
This system is not perfect, and indeed no litigation process is perfect; but it generally works.
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But what happens when the defence, for some reason, does not put in their own expert evidence?
The prosecution expert evidence will still be examined and cross-examined by lawyers – and the judge will still sum up, and the jury will still deliberate.
But the questions of the lawyers – especially the cross-examination – are not themselves evidence.
The only expert evidence is that put in by the prosecution.
The jury do not get to compare and contrast the expert evidence of the prosecution and the defence; the judge gets only to sum up the expert evidence of the prosecution.
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In the first Lucy Letby trial, for some reason, there was no expert evidence put in by the defence.
We do not know that reason.
What we do know is that the defence team continued to act for her on appeal and so it would seem that their client is not dissatisfied with the conduct of the defence. This would indicate that there was, at least for their client, a good reason for not putting in expert evidence, else – presumably – she would have instructed new counsel for the appeal.
If so, could there be a good reason?
Yes, indeed there could be more than one good reason – though this is supposition, for we do not know the reason.
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One possible good reason for there not being expert evidence put in by the defence has been identified by the experienced criminal barrister Adam King in a strong piece setting out why there may be a miscarriage of justice in this case:
“One reason the defence might have chosen not to call Dr Hall (and I am speculating here) is if they felt they had so thoroughly undermined Dr Evans that they were better off leaving it at that. That would be a big tactical call, but covering your own back is not always consistent with protecting your client’s interests.
“So, for example: if your own expert would contradict much, but not all, of the Crown’s expert’s conclusions, and you believe the credibility of the Crown’s expert has been totally destroyed, you might judge it prudent not to put your own expert in the witness box. Avoiding the potential for future criticism and hindsight regret by putting your client in what you believe will be a worse position — by calling your own expert — is not a boss move. This is all speculation, but I guarantee that careful thought went into the decision not to call Dr Hall. None of this, though, would mean the conviction is safe.”
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Another possible reason not to call expert evidence is that your client’s case is that the relevant area of knowledge is such that no actual expertise is possible. This may be because of the lack of reliable data, or because it is a novel or developing area.
If so, calling an expert on that point would contradict that position.
We do know that Letby’s defence lawyers put in a detailed submission at the end of the prosecution case in the first trial that the prosecution had shown no case to answer and that prosecution expert evidence should be ruled inadmissible. It may have been that calling expert evidence would have undermined the prospects of what may have been a successful application.
We don’t know.
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In essence, the decision not to call expert evidence may have been a perfectly legitimate one for Letby and her lawyers to make in the circumstances of her case.
And one should remember – and this is a crucial point – it is for the prosecution to make out their case.
It is for the Crown to prove their case to the criminal standard of proof, and not for the defence to disprove it.
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But.
While it may have been in the interests of Letby and her lawyers not to put in expert evidence, this has the knock-on effect of there being no expert evidence from the defence for the jury to consider.
That prosecution expert evidence may be subject to robust cross-examination – but the questions of the barrister are not evidence, and the jury have to decide the case on the basis of the evidence.
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At this point, many legal folk and others would say that the fault here is with Letby and her lawyers. The defence had the opportunity to put in their own expert evidence, and they did not do so. And that the convictions were the consequence.
But it may be that response avoids a key issue.
It is for the prosecution to prove their case, and not for the defence to disprove it.
It is thereby for the prosecution to ensure that the expert evidence on which it seeks to rely is as sound as possible.
The prosecution cannot shrug off this responsibility and say that it can be cured by the defence expert witnesses.
And there is concern that the prosecution expert evidence in the Letby case was not sound to begin with.
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If that concern about the prosecution expert evidence is well-based – and this is a legal blog and not a medical or science blog, and so like many of you I have no idea – then the question is what, if anything, can and should the legal system do about it – especially when the defence (for good reason or bad) do not put their own expert evidence in.
Here there are rules on what experts can and cannot do and say, and on what their duties are to the court; here there are also rules on the admissibility of expert evidence; and there will also be cross-examination of the expert by defence lawyers.
There are safeguards.
But.
The key safeguard against poor prosecution expert evidence in our adversarial system is that the defence can put in their own expert evidence for the jury to weigh against it.
But when the defence do not do that (for good reason or bad) then there is perhaps a system failure of the adversarial system.
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Here one can (again) say that is the fault of Letby and her lawyers.
But even taking that (fair) point at its highest, there is a potential wider problem.
A lot depends on the soundness of the Letby conviction.
Indeed there is an important public inquiry which is predicated on the basis of the convictions being sound:
If, as some insist, the prosecution expert evidence in the Letby case was unsound, then any inquiry based on that expert evidence being sound will have challenges.
“MD” in the current edition of Private Eye sets out the implications:
“…[the] Thirwall public inquiry may inadvertently be derailed by experts who say under oath that Letby wasn’t stopped sooner because there were far more plausible reasons for the deaths than murder.”
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The cases involving Roy Meadow show that we should always be alert to the problems of expert evidence.
If – and it is an if – the prosecution expert evidence in the Letby case was unsound, then there is a hard question of what else the criminal justice system could/should have done when a defence does not put their own expert evidence.
Given her decision not to put in expert evidence, is it the case that she had the fairest trial possible in the circumstances?
Or is there something else the criminal justice system could/should have done in this case – and similar cases?
It may be that there is a lacuna here – and not one which is easy, or even possible, to address in our adversarial system.
In essence: what can a criminal court do in respect of unsound expert evidence when the defence elects (for good reason or bad) not to put in their own expert evidence?
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Thanks so much for this typically incisive piece. It’s a relief to read something that refrains from jumping to the end bit (typically, as you say, ‘That proves that X/Y is true/false!’) and instead pares back the veil of familiarity, custom and noise to reveal a little of the creaking, clanking works that drive the legal system we have, both so impressively well and so (occasionally catastrophically) imperfectly. Cheers!
Thanks as ever for the blog. It raises lots of interesting points.
One other reason for not calling a defence expert witness is to avoid a jury considering it. In turn, might that make it easier for an appeal against conviction to succeed.
If for instance, there was evidence of a large number of baby deaths in which Letby could not have been involved, because she wasn’t on duty, and this evidence hadn’t been brought before the original trial, that would be a stronger appeal case than if the original jury had considered and rejected that evidence.
There is a real flaw in our current system when it comes to anything statistical. As the Meadow’s cases showed, courts aren’t very good at coping with probability, and the fact that given a big enough population and and underlying set of natural causes (in this case, that infants were already ill – hence being in hospital) bad things will happen which could be coincidence but look like they are linked. Courts don’t look at the bigger picture – they only look at the individual case.
An excellent point, though I would take it a little further and say that not just courts, but most people (including many doctors) are not good at coping with probability. Indeed, this is the main thesis behind Gerd Gigerenzer’s book, ‘Risk Savvy—how to make good decisions’.
Probability is not always—and is often not—intutive. If you don’t believe me, look up the Monty Hall problem (it’s on Wikipedia). Most people come away from considering that with their thinking frazzled, (and that’s just considering three possible options!). It is to mental arithmetic what an optical illusion is to vision.
In this context, the “prosecutor’s fallacy” is particularly relevant. See, e.g., https://www.cebm.ox.ac.uk/news/views/the-prosecutors-fallacy
Absolutely. And I recommend The Drunkards walk mentioned in the piece, as a helpful accessable insight into statistics.
The Simpson defence countered evidence that OJ was physically abusive to Brown with the statistical fact that studies show only 1 in 3,000 wife beaters go on to murder their spouse. The Jury nodded in agreement.
But this did not represent the case before them. Brown was murdered – if a murdered wife was beaten by her husband what is the probability that she was murdered by the husband? 90%
> “One other reason for not calling a defence expert witness is to avoid a jury considering it. In turn, might that make it easier for an appeal against conviction to succeed.
If the defence decided against using some evidence at trial, they wouldn’t be allowed to use that evidence to appeal a conviction.
Correct.
I’m puzzled by this. I read today that Oliver Campbell had his conviction quashed thanks to “fresh” expert evidence.
“The principal reason for our disquiet arises from the fact that the fresh evidence would provide a court with the benefit of much more information than was available at the trial about the appellant’s mental state when he made his confessions.
“As a result of the fresh expert evidence, the whole approach to the case would now be informed by a different and better understanding of relevant factors.
“Even if all the evidence of confessions were admitted, a jury knowing of the fresh evidence would be considering the reliability of those confessions in a materially different context. In those circumstances, we cannot say that the fresh evidence could not reasonably have affected the decision of the jury to convict.
“On that narrow but very important basis, we have concluded that the convictions are unsafe.”
Is the difference here that the expert testimony in the Letby case was withheld, and so would not be considered “fresh”?
In the case you mentioned it was an expert witness presenting new evidence. There isn’t new evidence in the Letby case, just expert challenges to the evidence presented at trial.
I have a scientifically attuned mind and have a great deal of trouble trying to apply it to ways of law, despite both being disciplines devoted to truth finding. While science got it’s head around statistics a century or two ago, law still seems resistant to bringing in subject matter experts who can state probability estimates and point out the fallacies we might make when making inferences about data. I would make expert evidence the responsibility of neither prosection nor defence but would remove it from the vagiaries of adversary influence, not least because experts don’t actually know the best way to explain their knowledge to the layman/jury and could do a better job if a judge were to elicit from them relevant details that would help the jury make sense of other evidence – expert evidence is not evidence in itself, it is insight about the data and how to consider it. Let the judge employ the experts to investigate complex evidence whichever side it comes from and then provide the court an opinion on it which both sides can cross examine.
The Post Office Inquiry has demonstrated another issue with the use of expert witnesses: viz. when the witness is not actually expert!
“Expert Witness” is a label that should be earned not annointed. Having sat on Juries – I do not have faith in the Jury system – even if Council or Justice’s summaries are fair and instructions precise, jury members are free to ignore or disagree with them. Bias such as misogeny and racism take over, most of the group look to the ‘Alphas’ for guidance.
Would I regard someone who touted for business, ignored important facts and cherry picked their past performance (success lies in our ability to write our own reviews)? No, and I would be prepared to argue the point against the eleven others staring me down while their chose leader explains my folly: “You’re entitled to your opinion, but you can’t ignore the expert’s qualifications, experience and expertise, which he expertly displayed.”
The Judge would then offer a majority verdict.
I don’t know the fuul facts of the case and I do not have a view or whether Letby is guilty, but I do know that even if the Judge decided to instruct the jury to disregard the entire body of evidence given by the Expert Witness, there is no mechanism to ensure that it is disregarded by the jury as a whole.
Two other considerations in all this:
1. Why doesn’t the criminal justice system follow the civil justice system, post-Wolf? Given that expert witnesses are serving the court, not their instructing lawyer, why not require the defence & prosecution experts to consider the evidence together, and settle which bits they agree on, and which bits they disagree on, leaving only the latter to be considered in court? Would that not save a lot of time?
2. When is an ‘expert’ not an expert? In rare situations, there may be no senior professionals in the relevant discipline who have encountered the matter in question. it then becomes a matter of exchanging opinion, via rhetoric. Politics has shown us how productive this mechanism is as a decision tool, usually in the ensuing blunder.
To your first point: there is a mechanism for pre-trial meetings between opposing experts in both the criminal and civil proceedings – CtimPR 19.6. It can be voluntary but also court-ordered. I have been involved in many such exercises.
I am no lawyer but it seems to me that the expert witness system has serious weaknesses. Following the Post Office/Horizon affair, a lot of problems seem to have arisen from misunderstandings – by the courts as well as individuals – of the role and competence of expert witnesses.
I would be interested to know if European independent ‘inquisitor’ functions work better than the UK/US Common Law approach? The latter seems to depend too heavily on which side can instruct the most ‘powerful’ expert.
For the last 30 years I have acted as an expert witness, instructed on occasion by both prosecution and defence. I stress I don’t know much about the Letby case.
The main reason I haven’t been called by defence counsel in some cases is that my evidence wouldn’t have been helpful, either because I couldn’t sustain the arguments that were hoped for when I was instucted or I would otherwise be vulnerable in cross examination, bearing in mind my over-riding duty to the court.
But that doesn’t mean my involvement was useless. I will have conducted a due diligence exercise which at the least helps persuade a defendant that they have had proper attention. But I may also helped craft cross-examination questions for defence counsel to put to the prosecution expert. I may even be in court to assist, even if silent.
How much this applies to Letby of course I don’t know.
Really useful contribution. It strikes me that the purpose of a defense Expert Witness is to either counter the evidence of a prosecution Expert, perhaps to ‘dial down the certainty and confidence’; or to provide a credible counter narative.
The American ‘Grand Jury’ offers the defence and prosecution an opportunity to test their cases in pre-trial and prepare counter-factuals.
I wish to correct a misapprehension about grand jury practice in the US.
The general rule in the US is that an accused has no right to testify before a grand jury. Indeed, in the overwhelming majority of cases, especially at the state and local levels, the only evidence presented is that of the police investigation. It would be most unusual for an expert witness, whether testifying for the prosecution or the defense, to appear before a grand jury.
https://scholar.google.com/scholar_case?case=15938389737466632088
My point is that the Grand Jury and (I forgot to mention) deposition process act a filters to triage a case before a trial.
Thank you for your enlightening comments on R v Letby. If the judge thought the evidence of the prosecution expert unsatisfactory, could he, of his own motion, appoint an expert as amicus curiae?
As far as I know there is no provision for judges to appoint experts to support their decisions but maybe there should be. I specialise in digital evidence and have seen judges struggle with some of the decisions they need to make. In a recent set of cases judges had to decide whether particular messages were being captured from storage on mobile phones (in which case they were admissible) or in the course of transmission between phones (which would make then inadmissible under s56 IPA 2016). Examining what was actually happening is not straightforward but judges made up their minds unaided by access to advice of their own. There are other situations where judges have to decide whether to grant public interest immunity to stop disclosure of advanced technical means of. evidence acquisition. They have to balance that against the requirement for a fair trial. Again, they seem to do this without access to external expertise.
I am no lawyer but I believe a Judge may have an Assessor in an appropriate case. That would be less useful in a jury trial.
“… the defence team continued to act for her on appeal and so it would seem that their client is not dissatisfied with the conduct of the defence. This would indicate that there was, at least for their client, a good reason for not putting in expert evidence, else – presumably – she would have instructed new counsel for the appeal.”
I have a doubt about this part. The “presumably” there rests on Letby having the understanding and resourcefulness to be making those kinds of judgements about her defence. Intuitively I don’t feel sure she’s equipped for that. Being either a conscientious nurse plunged into a nightmare, or a disturbed murderous nurse in a nightmare of your own making, is a very different mindset from being on top of legal stuff and ready to boss your lawyers about. I think she could easily be very reliant on other people’s advice.
Thank you, David. In general I’m of the view that, particularly now that scientific evidence more often forms part of the evidence in a trial, and given the general lack of scientific knowledge (perhaps all three of judge, jury and counsel) some independent dimension is required, such as a technical consultant able to interrogate scientific evidence for the benefit of the court as a whole ..
But the thing that troubles me in your analysis is in this passage:
‘This would indicate that there was, at least for their client, a good reason for not putting in expert evidence, else – presumably – she would have instructed new counsel for the appeal.’
I’m not sure that takes into account what we might call the clutched straw aspect of a defendant’s choice to appoint a particular solicitor, or to choose a particular defence strategy. It seems that family trust in a solicitor with minimal criminal experience has played a role here. Understandably neither Letby nor her family are experienced in the conduct of a criminal defence, and all are deeply suspicious of pretty much the world at large. I think there’s a chance that they simply clung to their defence team for the appeal out of little more than desperation and a sense of social trust having been destroyed (which is the central element in what Jonathan Shay describes as the social consequences of PTSD – I have no idea if Letby or family have a formal diagnosis of PTSD, but can well appreciate she may have a strong sense of having been betrayed).
Not that I’ve a clue how such a problem might be addressed. Nor do I have any real insight into the work of those who provided Letby with psychiatric support, or made a judgment of her fitness to stand trial. Just that there must also be a question of, in effect, competence to instruct.
No straws clutched, but I fear a strawman created nonetheless?
As a former Chairman of the Society of Expert Witnesses, I would question your assertion, “It is thereby for the prosecution to ensure that the expert evidence on which it seeks to rely is as sound as possible”. A sound witness supports those who call him/her. An Expert has a duty to his or her Expertise. “In the country of the blind, the one-eyed man is king”; her late Majesty and her father have demonstrated that monarchy is duty and service to the public As a witness the Expert has a duty of candour – as has every witness – of objectivity and, a fortiori when unopposed, neutrality. Absence of those duties, often found among those whom a regular client instructs, can lead to miscarriages of Justice – cf the P.O. Horizob Inquiry.
“The Expert Witness has a duty to his or her expertise.” Indeed, but that expertise will always be limited by human knowledge and fallibility. However devoted an Expert Witness may be, they may not have sufficient expertise to survive cross examination by a well informed defence barrister. There will be a number of experts in the field the prosecution can call upon and it is up to them to select the best for their client. The devotion to duty of each Expert is not in question.
Unfortunately in this case the experts were not basing their testimony on scientific facts. Absolutely no other potential (of which there were many) causation of symptoms were given or explored . Absolutely zero methodology of how they had reach their conclusions, what was ruled out , why and how. It felt like they were plucking diagnoses, methods of harm out of a magic hat.
Question may of the babies in the case had post mortem and inquests with clear cause of death, how does a so called expert who’s not worked in clinical practice for 15 years, get to change the outcome. Seems somewhat ludicrous to me.
In your penultimate paragraph you note a potential weakness that may be difficult to resolve in an adversarial criminal court process.
This adversarialness, and its binary nature, also has resonances in the binary nature of verdicts. Someone is either completely innocent – completely exonerated – or completely guilty.
In a case like this, one can imagine that a more nuanced range of verdicts might be useful. For example ‘not proven but highly suspicious’.
The Scottish system has such a system, and that caused its own problems: https://www.bbc.co.uk/news/uk-scotland-glasgow-west-65394103
I am not a lawyer or even a legal expert, BUT it seems to me that if we grafted elements of the innquisitorial system into or onto the adversarial system, the Judge could have called additional expert witnesses if he/she was satisfied that the prosecution case had flaws and in the knowledge that the defence were not going to call any expert witnesses.
At least both sides would have been given the opportunity to examine the court expert as would the judge and this MAY have highlighted the unsafeness of the prosecution expert evidence – at least sufficiently to have cast a reasonable doubt in the minds of the jury or to bolster and make good the flaws in the prosecution case. As David says expert witnesses are bound to the court – not the lawyers who employ them, as such there is supposed to be a degree of independence in expert testimony. Allowing the judge to call expert witnesses to the case would amplify this by overcoming the intentions of the defence in not calling expert witnesses.
I am not arguing that a judge must call additional witnesses expert or otherwise in every case. I am not advocating the abandonment or bastardisation of the adversarial system, rather, a tweak where an experienced judge could prevent an unsafe conviction from occuring in the first place.
So, we stage a medieval joust, let the heralds sound and on the battlefield we have a somewhat feeble looking girl, an unknown as her champion and arrayed against her, a rich panoply of knights and clerks with swords and scrolls drawn. That how we do things here, that is the model on which our legal system is based.
Small wonder that when the girl and champion don’t put up much of a fight we feel a bit queasy. We must say ‘this lady has had her day in court, we must assume her champions were adequate to the job’. Ignore dark mumblings from the audience.
We might think that in a medieval joust the stewards would kick inadequate champions off the battlefield and call for more adequate ones, if only for the spectacles sake. Our modern equivalent does not do that and leaves loose ends that might yet unravel the cloth.
I am left with a niggling what if. What if the real problem was a malign hospital management system with a bit of high level incompetence and underfunding helping things along. A well organised cover up and a bit of corporate omerta go a long way. Such a thing could not happen here – could it.
As I understand it, Lethby was not convicted solely on statistical or circumstantial evidence. The uncontroverted post-mortem scientific tests demonstrated at least some of the dead neonate infants were found to have been injected with insulin sufficient to kill them, while they were under her care. They were murdered. They question is who did it. The jury was convinced it was Lethby and not some other unnamed perpetrator.
Likewise, Shipman was convicted for killing 15 patients. In many of those cases, there was evidence of overdoses of morphine. But not all, for example the remains of Maria West had already been cremated. Nonetheless, her death led to one of the murder convictions. We don’t need to test all 200+ of the elderly people who died in his care to accept the result of the inquiry that he killed them, even if the evidence in all cases would not be sufficient for a criminal conviction.
I would be interested to hear if the unusually high number of neonatal deaths at the Countess of Chester Hospital continued after Lethby was arrested, or if the problem abruptly ceased.
Having spouted off earlier, I now understand that the cases of insulin poisoning were *attempted* murder. (One of the dangers of commenting without reading all the background papers.)
That does not change my point much. There was scientific evidence of an attempt to kill, and the jury convicted Letby. It is not a great leap to conclude that other somewhat similar allegations are also true but that is a matter for the jury.
If the insulin related to attempted murder, then I assume that the evidence came from sources other than postmortems. To then assume that postmortems without evidence of insulin poisoning should be ignored in convicting for murder of those people who died sounds……….iffy.
The sample with a positive test result for insulin was not tested in a forensic laboratory and interpreted carefully by a toxicologist. The result of the test – a less accurate test than what a laboratory uses – was recorded and then the sample was discarded. It’s not very reliable evidence that there was an unusual amount of insulin. And like everything else in the case against her it wasn’t proof that she specifically was responsible.
Your assertions are still not accurate.There is no valid scientific evidence of an attempt to kill. The correct tests for insulin were not performed and the so called medical expert was not an expert in this area. Many experts are now of the opinion that no crimes were committed. In response to your question about whether deaths reduced after Letby stopped working, it is important to be aware that the unit stopped taking very premature and vulnerable babies at that point so there would as a result be a consequential reduction in deaths. It has also been suggested that the increased number of deaths during the period in question was not in fact statistically significant. I would maintain that the evidence was completely circumstantial if at all.
I can only say that, from what I have read in the various articles questioning the verdict, including comments from expert statisticians, that I agree the conviction is unsafe and needs to be seriously re-examined. There are too many questions hanging over this to be sure that Letby is guilty.
There seems to me one procedural point that doesn’t seem quite logical: the idea that an expert witness is formally an agent of the court, rather than of either party, yet the choice of calling them or not calling them to give evidence is left to one of the parties.
If the system is to be that a neutral agent of the court is nevertheless chosen by one side or other, surely it would make sense that, once that expert witness has been chosen to prepare evidence by either side, that evidence (whatever it turns out to say) now belongs to the court and will be heard, and cross-examined, regardless of the wishes of either party? The court’s witness, if you will, rather than either party’s.