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Experts warn Letby inquiry of misreading stats to explain 'suspicious' deaths

thejusticegap.com

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Re: Experts warn Letby inquiry of misreading stats to explain 'suspicious' deaths

#31

Post by notahacker »

Marazan wrote: post #20
rwmj wrote: post #11

While the statisticians are right to be cautious about clusters of deaths => serial killer, we also have to remember that a 9 month trial presented lots of evidence to a jury, they deliberated for over a week, and returned seven guilty verdicts. Unless you were also sitting at that trial or have read every line of court transcript, it would be very unwise to start claiming there's a miscarriage of justice.

Yeah, this is not a case of someone being convicted based on dodgy statistical data. Indeed she was found not guilty on a large number of other deaths. There was corroborating evidence which lead to her conviction.

Not to mention the fact the background was the complete opposite of a statistical witch hunt. The overlap between Letby and abnormal baby collapses and deaths and her strange behaviour around them had been noted by several colleagues, but hospital management stuck doggedly to the null hypothesis that it was just bad luck and resisted attempts to investigate even after moving her to other duties (at which point the unexpected baby collapses stopped)

Re: Experts warn Letby inquiry of misreading stats to explain 'suspicious' deaths

#33

Post by crote »

rwmj wrote: post #11

While the statisticians are right to be cautious about clusters of deaths => serial killer, we also have to remember that a 9 month trial presented lots of evidence to a jury, they deliberated for over a week, and returned seven guilty verdicts. Unless you were also sitting at that trial or have read every line of court transcript, it would be very unwise to start claiming there's a miscarriage of justice.

To a large extent they didn't have to involve statistics. There was plenty of better evidence in the Letby case.

However, the public perception around the time of the trial was substantially different. Especially early on, the media focused strongly on the fact that it "could not possibly be a coincidence". Reading the trial coverage I got a very strong feeling of déjà vu, seeing the coverage pretty much mirroring the Lucia de Berk case.

Considering the mountain of other evidence in the Letby case, I highly doubt it was a miscarriage of justice. But I definitely agree with the Statistical Society that just because something looks like a duck, it doesn't have to be a duck.

Re: Experts warn Letby inquiry of misreading stats to explain 'suspicious' deaths

#34

Post by crote »

kitd wrote: post #16
brvsft wrote: post #5

> There are obvious parallels with the Lethby case. Statements in de Berk’s diary about ‘a very great secret’ and a ‘compulsion’ on a day that a patient had died were given a sinister interpretation. They didn't include any examples of the parallel. This goes over some of the notes: https://www.theguardian.com/uk-news/2022/oct/13/lucy-letby-p... > On another, she wrote “I am a horrible evil person” and on another in…

On the afternoon of the conviction, there was an expert criminal psychiatrist on BBC radio who had been following the trial closely. Apparently those notes, though they made all the headlines, played little part in her conviction, and are typical for someone suffering stress &| depression. The thing that did for her apparently were messages she had sent some of the parents, the times of which contradicted her testimo…

That's a very good reason to warn the public about it, is it not?

People generally do not read court transcripts, they read media headlines. It's basically a guarantee that some people are already convinced their statistically unlucky coworkers are also serial killers. It can easily lead to witch hunts.

Re: Experts warn Letby inquiry of misreading stats to explain 'suspicious' deaths

#35

Post by pbhjpbhj »

randomcarbloke wrote: post #9
piker wrote: post #2

Anybody who closely followed this case who could identify for the readers here any direct evidence of these crimes, or should we read this article to imply Lucy herself might be innocent?

She kept notes, apparently there was an abundance of evidence in her home, doctors had raised concerns. This isn't a case of relying solely on data, rather the data bear out what everything else suggests.

IIRC, doctors/administrators dismissed statistical evidence as "it couldn't be lovely Lucy". Whether it was possible to make statistical inferences probably speaks more to whether the family's have a case against the hospitals/health authorities for neglect, eg neglecting to follow up on suspicions.

Re: Experts warn Letby inquiry of misreading stats to explain 'suspicious' deaths

#36

Post by crote »

piker wrote: post #2

Anybody who closely followed this case who could identify for the readers here any direct evidence of these crimes, or should we read this article to imply Lucy herself might be innocent?

I recommend reading the Wikipedia page, the "2023 Trial" section has a pretty good overview.

Re: Experts warn Letby inquiry of misreading stats to explain 'suspicious' deaths

#37

Post by contravariant »

DanBC wrote: post #29
contravariant wrote: post #28

Earlier quoted context omitted.

I suppose, but it wouldn't be the first time a judge or jury was swayed by dubious statistics. At least that is exactly what happened to Lucia de B [1] (which they mention in the article), which at first glance looks eerily similar. [1]: https://en.m.wikipedia.org/wiki/Lucia_de_Berk

The difference is that statistics were used in de Berk's prosecution, but were not used in Letby's prosecution.

Just implicitly assuming that something couldn't have been chance is just trying to do statistics on pure intuition, which is notoriously difficult.

Though unlike the Lucia de B case it doesn't seem likely these deaths could all have been natural. The evidence pointing towards Letby seems mostly probalistic in nature though, which should be treated carefully.

Re: Experts warn Letby inquiry of misreading stats to explain 'suspicious' deaths

#38

Post by d1sxeyes »

DanBC wrote: post #7
piker wrote: post #2

Anybody who closely followed this case who could identify for the readers here any direct evidence of these crimes, or should we read this article to imply Lucy herself might be innocent?

> or should we read this article to imply Lucy herself might be innocent? No, the point being made is that a murderer was able to evade detection because her employing organisation did not understand the data they had, because they did not understand statistics.

I don’t think that’s the point either. I think the point is “be very careful jumping to conclusions, and just because you may find patterns similar to those in this case elsewhere, that does not mean that we are necessarily dealing with another serial killer”.

Re: Experts warn Letby inquiry of misreading stats to explain 'suspicious' deaths

#39

Post by rgrieselhuber »

rwmj wrote: post #11

While the statisticians are right to be cautious about clusters of deaths => serial killer, we also have to remember that a 9 month trial presented lots of evidence to a jury, they deliberated for over a week, and returned seven guilty verdicts. Unless you were also sitting at that trial or have read every line of court transcript, it would be very unwise to start claiming there's a miscarriage of justice.

Also “experts warn” is argumentum ad verecundiam.

Re: Experts warn Letby inquiry of misreading stats to explain 'suspicious' deaths

#40

Post by ssl232 »

quietbritishjim wrote: post #13
rwmj wrote: post #11

While the statisticians are right to be cautious about clusters of deaths => serial killer, we also have to remember that a 9 month trial presented lots of evidence to a jury, they deliberated for over a week, and returned seven guilty verdicts. Unless you were also sitting at that trial or have read every line of court transcript, it would be very unwise to start claiming there's a miscarriage of justice.

Those arguments included that the suspicious deaths all lined up perfectly with Lucy Letby's shifts, that she was often caught interacting with those babies when she had been instructed not to, and that when she was taken off the ward the deaths instantly stopped. That is a level of causality checking far stronger than most Bayesian analyses.

I went down the rabbit hole on this a couple of months ago. Some of the details are a bit hazy in my memory now as it was about 2 months ago, but in the interest of playing devil's advocate...

> the suspicious deaths all lined up perfectly with Lucy Letby's shifts

Once a nurse has been around the ward for long enough to have seen several deaths, you can produce a table showing a set of baby deaths correlating to any nurse's shifts [1]. The ward was for seriously ill newborn babies, so baby deaths were unfortunately common, and each nurse would regularly be on shifts where one would die.

As you say, these deaths were considered "suspicious", but some (e.g. [2]) claim otherwise, saying key tests that would rule the accused method of murder in or out were not done at the time of death.

> she was often caught interacting with those babies when she had been instructed not to

(Again, playing devil's advocate) the job selects for nurses who (apart from Letby, it seems) deeply care for young babies. Not a smoking gun.

> when she was taken off the ward the deaths instantly stopped

This has been contested. As far I can tell the hospital's death rate statistics disagree with the Office for National Statistics. The latter's data appears to show the deaths peaked after Letby was taken off the ward [3] (note, I haven't checked the underlying source mentioned in the tweet).

Replies to some comments below yours:

> And she took home documents from several of those patients, which she'd have no ordinary reason to have fished out of the trash.

Apparently this is quite common for nurses working on this and other intensive care wards. Nurses just off duty are often phoned by the nurses who took over the shift, asking for details on particular babies' treatment or behaviours that day. Having files on the babies to hand would let Letby give exact details without having to remember or misremember them.

> And the little old thing that she wrote "I killed them on purpose" on a post-it-note at her house.

This looks bad, yes, but again not a smoking gun. I think I read this happened after she was already taken off the ward or had somehow found out she was under investigation for causing baby deaths. I could believe a note like that could be written by someone on the verge of a breakdown or under extreme stress. The "I killed them" bit I could believe someone could write if they regret not having spotted something earlier that someone more experienced might have, especially if they have imposter syndrome.

As the blog makes clear, it's not really about whether Letby is innocent or guilty, it's about whether she got a fair trial. It seems many statistics were misused in her case, circumstantial evidence was used as smoking guns, and some evidence was not fully addressed [4]; basically enough to question the verdict.

[1] https://twitter.com/profnfenton/status/1692837686166368660

[2] https://gill1109.com/2023/05/24/the-lucy-letby-case/

[3] https://twitter.com/LawHealthTech/status/1692917506078376019

[4] Apparently during the trial it was mentioned that sewage pipes crossed the ceiling and backflow sometimes came into the sinks. Definitely not a good mix to have in a ward with very ill babies. Hopefully infection spread from bad plumbing was fully ruled out as causes of death during the trial. Some critics don't seem to think it was.

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