Lucy Letby

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“We’ve found a witch. May we burn her?”

— Monty Python and the Holy Grail

On herd minds, groupthink and narrative biases

Lucy Letby’s case is in the news. On 24 May 2024, the Court of Appeal denied Letby leave to appeal against her conviction. Neither the grounds for the appeal nor the reasons for refusal are yet public. On 10 June, her retrial for the attempted murder of “Child K” began in Manchester. But on 13 May 2024, New Yorker magazine published A British Nurse Was Found Guilty of Killing Seven Babies. Did she do it?, a 13,000-word investigative piece by Rachel Aviv that questioned the the safety of Letby’s original convictions. The piece was loosely geo-blocked in the UK, ostensibly to avoid contempt of court during the retrial. But it is not hard to find online, and it ran unedited in the New Yorker’s UK print edition, so there may be some canny “Streisand Effect” marketing at play here too. It raises its own questions about the practicality of sub judice rules in the age of the world-wide internet, but that is a discussion for another day.

Those with a passing acquaintance of the case tend to suppose that, having been convicted of multiple infant murders, the case is closed and she must be a monster. She admitted everything in a note, right? But look a bit closer and the picture is complicated. The note is not the unequivocal confession it has been made out to be. There is no direct evidence. Each piece of circumstantial evidence, in isolation, is ambiguous. The strength of the case of conviction appears to have emerged from the preponderance of evidence, rather than subsisting in a particular smoking gun.

At this point there are two available narratives: Lucy Letby is either a person of pure, calculated evil, or the victim of a breathtaking miscarriage of justice. But these extremes leave untouched between them a vast range of ambivalent attitudes: We like our narratives to tell us things about the world, and a perspective that says, “well, it’s complicated” doesn’t tell us much about the world. It isn’t useful. So few of us occupy that space.

JC will advance the position that we should. While it may offer little intellectual satisfaction, it may be the best we can reasonably expect.

The system has behaved in a way which deprives this individual of a middle ground, in which she is an ordinary kid, with her pluses and minuses, virtues and failings, just like the rest of us: neither angel nor devil.

Given the probabilities at play — 99% of us are neither pure angels or devils, but somewhere along the continuum between — allowing Lucy Letby to sit at only one or other of these extremities seems an injustice in itself.

Confirmation bias

The problem with “angel” and “devil” narratives is that they become self-fulfilling: once you’ve settled on one, you can panel-beat most subsequent information to suit that view. The hard-edged peripheral evidence we do have abut Lucy Letby can and has been coloured through that lens. For example, Letby’s social media activity: here is BBC reporter Judith Moritz, in a piece to camera, on reviewing Letby’s social media posts:

“Sparky, full of fun, popular — she looks like the life and soul of the party in these photos. I don’t know what Britain’s most prolific child killer should look like — I’m pretty sure it’s not this, though.

And then a few moments later:

“She comes across as — mousy; a bit normal — you can’t really marry that with the enormity of what she’s been accused of.”

If — and only if — we are already persuaded of her guilt, her vivacious personality and active social life notwithstanding this mark her out as a psychopath. It corroborates and amplifies her wickedness. If we believe her to be innocent, that she has been convicted despite her vivacious personality and active social life — what sort of serial killer is like that? — only illustrates the single-mindedness with which a vicious criminal system will crush an innocent, unsuspecting spirit.

But from a neutral perspective, this behaviour is normal. It tells us nothing. It places Lucy Letby in that ordinary space, with the rest of us, within a standard deviation of the mean. It neither proves nor disproves anything. There have been very, very few serial-killer nurses. We have no evidence about what, as a rule, they are like. In any case, it is neither direct nor circumstantial evidence of her perpetration of the crimes with which she has been accused.

In the language of the criminal law, then, this social media activity has low “probative” content — it doesn’t prove anything — but high “prejudicial” value — it colours any existing preconceptions a jury might hold. A court may exclude this evidence if “its prejudicial effect is out of proportion to its probative value”.

Similarly, that Lucy Letby searched online for the parents of the deceased is consistent with either breathtaking malevolence — if she is a serial killer — or affecting compassion — if she is not. By itself, it is evidence of neither. We all Google individuals we meet in real life — even people we know we probably shouldn’t: this is perfectly normal behaviour. We are curious animals.

The mechanisms by which we process information are biases — confirmation bias — a well-documented logical fallacy where we frame any information to validate what we already believe — or its less-understood converse: ignorance bias, where we tactically ignore information that does not support, or tends to contradict, our working theory.

Both biases are in play whether we believe Lucy Letby is a serial killer, or the victim of a grave injustice. Both standpoints are equally emotive.

There is no comfortable centre to hold here.

Standpoint intersection ahoy

Speaking of narratives there are many at play here. Criminal justice stands at the intersection of at least four discrete fields of intellectual enquiry: law, medicine, statistics and ethics. They are not commensurate — each has its own rules, customs and institutions and authority in one does not commute to the others. In a perfect world their outcomes would converge, but the world is not perfect. There will be circumstances in which the correct legal outcome is not morally right, the correct moral outcome is not borne by the statistics, the statistics are at odds with our knowledge, and vice versa. There is little wonder good people get upset with each other.

There is even room for epistemology. You cannot but frame your understanding of the overall scenario through one or other of those prisms. Or a combination, but that is liable to lead to conflict. There is no transcendent, neutral frame of reference by which the others may be judged. Without a framework the territory is random, incoherent noise.

For the scenario is one that unusually uncertain, about which the prospect of consensus is unusually low. It is not even clear that there was a wrongful killing here, let alone by whom.

Victims

Emotions are already aggravated; the stakes are raised yet higher by the undoubted loss and grief of the families of lost infants. But we must realise that their grief is unavoidable and attaches to their loss which is the same whatever its cause. That they are bereaved is not at issue: the question is why: Lucy Letby’s acquittal does not postpone or deny them justice for their loss: no injustice may have been done. Nor does her wrongful conviction given them justice: that your child was murdered it is surely a heavier burden to bear than she died unavoidably of natural causes.

So advocating for Lucy Letby’s innocence should be no affront to the grieving families: one can respect their unimaginable grief and, in some way seek to ameliorate it, by arguing her case.

Substance, form and process

The first thing to bear in mind is the difference between the substantive — the morally unjustified ending of a life (this is an ethical frame of reference), the formal — the commission of the act of “murder” as defined in law (in some ways an ethicist’s map of the territory: a systematic way of economically delivering that ethical framework), and the procedural — the process one must gone through to determine whether a murder was committed. This “procedural” includes the presumption of innocence, the adversarial tradition of British criminal justice, the laws of evidence, the rules of court procedure, and tactics and strategies that defence and prosecution teams adopt within that milieu to best present their case, whose outcome is ultimately determined not by judges, lawyers, ethicists, statisticians, physicians or metaphysicians but by 12 ordinary people, drawn at random from the electoral roll, who may have none of these skills.

These are different questions, with different considerations, and it is important they are not confused. A person who murders unobserved in cold blood, leaves no evidence, and has no motive cannot be convicted beyond reasonable doubt of murder unless no other explanation is possible. The procedural element fails: there is not enough evidence. A person who kills in cold blood, before witnesses but in demonstrable, reasonable self-defence, cannot be convicted of murder because the formal elements are not met. She has a defence.

Our justice system is meant to benefit the accused in marginal cases: acquitting the occasional perpetrator is a “lesser evil” than convicting a single innocent.

But even then we get it wrong sometimes.

The medical misadventure cases

Indeed, cases involving medical misadventure, no direct evidence and which rely on statistics are a recurring case of injustice: Sally Clark, Daniela Poggliera and Lucia de Berk are but three recent examples with strikingly similar facts patterns. We should not take concerns about statistics lightly.

Where there is no “direct” evidence, the form and procedure becomes all the more important.

In Lucy Letby’s case no direct evidence definitively links her to a single murder. No direct evidence unequivocally suggests there was a murder — as opposed to misadventure, negligence or even inadvertent accident — at all. Each case, taken in isolation, could be plausibly explained as a natural death. But by the same token nor is there unequivocal evidence that any of these were not murders, nor that, if they were, Letby did not commit them.

The internet is polarised around two highly unlikely contingencies.

It is logically possible she did commit the murders, logically possible she did not, and logically possible she played a role in some or all of the deaths that did not amount to murder.

The question of whether she should be convicted comes down, at some point, to an estimation of probabilities. These inform how “sure” one can be about the proposition “defendant murdered victim”.

These murder cases have an unusually wide range of unknowns. In isolation , we cannot say whether there was any murder at all. The deaths could have been innocent, and they could have been culpable to some legal standard short of murder (negligence, for example)

Emergence

There is a kind of meta-statistics at play here, too. For even if there is reasonable doubt for every individual case, the unusual repetition of cases creates its own meta narrative.

Roll once and get a six, and there is no surprise. That outcome was as likely as any other. Roll three sixes and it becomes a lot less probable: you would expect that only once in two hundred and sixteen times. Unusual, but nothing yet is seriously amiss. But roll ten consecutive sixes — a probability of less than one in sixty million — and you should start inspecting your die.

This is the essence of the prosecution case against Lucy Letby: that while each of the deaths that occurred on her shifts was in itself explainable, a sheer number of consecutive deaths on her shift were not.

Unlike in Sally Clark case, prosecution did not e

Each of these enquiries requires an answer “beyond reasonable doubt”. If a victim dies in the presence of a single person with a means and motive, such that if the death was intentional there is no other possible suspect, if there is a reasonable doubt as to the death being natural — even if it probably was not — there can be no conviction.

“Once is happenstance. Twice is coincidence. Three times is enemy action.” — Ian Fleming, Goldfinger (1959)

Here is where a sequence makes a difference. One such occurrence might be improbable, five occurrences extremely improbable, 500,

So

What are the percentages of serial killers with history of broken homes, physical or sexual abuse, and mental illness? What percentage are female?

“God complex”

Killing people is not evidence of a God complex. The basest criminal can take life. Bringing people back to life — that is evidence of a God complex.

Evidence

Insulin “smoking gun”

In two cases (Child F and Child L) lab tests indicating high levels of insulin without accompanying c-peptide, which is prime facie evidence of administered insulin (naturally occurring insulin is accompanied by c-peptides; artificially administered insulin is not). Insulin was not prescribed for either infant. If it was true that insulin was added without prescription this is evidence of actual human agency in these two episodes.

The defence team accepted the prosecution’s claim that insulin was added to parenteral nutrition bags and it was presented to the court as an agreed fact.

• The test in question was not reliable for factitious insulin. From the label:

“Please note that the insulin assay performed at RLUH is not suitable for the investigation of factitious hypoglycaemia. If exogenous insulin administration is suspected as the cause of hypoglycaemia, please inform the laboratory so that the sample can be referred externally for analysis.”

• The test results seem to indicate very high levels of insulin: 4657 pmol/L is about four times a dangerously high level in an adult. While, yes, this is what you might expect a murderer to try to do —
• Both babies recovered: You might expect premature babies registering such high insulin levels — four times a critical level for an adult — might have at least caused a fuss at the hospital. But not only did the babies make a full recovery, with no record of hypoglycemic coma, but —
• No-one even noticed the high insulin in their tests until 2018: That is, three years after the babies made a full recovery. If you are looking for a res ipsa loquitur about these events, can we suggest that this is as indicative of negligence in the clinical staff administering the test, or the self-professed unreliability of the tests for detecting factitious insulin.

The Texas sharpshooter

See the TriedbyStats website: Over 730 shifts, with 38 “suspects” If you self-select one

The victim’s families

There are unquestionable victims here: the families. If Lucy Letby wasn’t responsible then this was either an unavoidable accident, in which case, there is no closure, or there is another culpable explanation — an alternative murderer seems extremely implausible — but medical misadventure of some kind is not. Difficult

The post-it note

Everyone seems to accept the notes are highly inclusive and of little evidential value.

“The ramblings of someone under extreme psychological pressure.”

Resources

Online

• That New Yorker Article (choose your own snapshot from the Wayback Machine)
• Mephitis - The Lucy Letby Case May In Time Be The Story Of The Century
• TriedbyStats
• The Insulin ‘Evidence’ in the Lucy Letby Trial. Criminal Justice in England: Disagreeable Facts

Podcasts

• We need to talk about Lucy Letby (Peter Elston and Michael McConville podcast)
• The Trial of Lucy Letby (Daily Mail podcast)

See also

• Miscarriages of justice