The Law and Policy Blog

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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