5 ms·

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 evid

by rwmj 3y ago

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.

iudqnolq 3y ago
edit: wrong, can't delete
- deleted 3y ago
  [deleted]
quietbritishjim 3y ago
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.
- automatic6131 3y ago
  And she took home documents from several of those patients, which she'd have no ordinary reason to have fished out of the trash.
  - frou_dh 3y ago
    And the little old thing that she wrote "I killed them on purpose" on a post-it-note at her house.
    - ad404b8a372f2b9 3y ago
      Ah jinx!
    - kitd 3y ago
      Those notes had little effect in her conviction apparently, according to a criminal psychiatrist on BBC radio. It is behaviour typical of someone suffering depression, for which she was having treatment at the time.
      - adammarples 3y ago
        Writing "I killed them on purpose" is not typical behaviour of depressed people.
        kitd 3y ago
        I'm going by the testimony of a psychiatrist who had been following the trial. Depression can apparently push people into a mental world where everything is at rock bottom and what gets written is just an expression of that.
        Intralexical 3y ago
        Most depressed people don't have strings of deaths following them wherever they go. It is not unexpected of depressed people to blame themselves for bad things that happen around them, I think. …For multiple reasons, (1.) because you really do hate yourself that much, and might view those tragic events as also personal failures, and (2.) because for the suicidally depressed, it can be a way to manufacture a reason to believe why you deserve to be hated or physically injured. IIRC the insulin levels or something were rather suspicious, but in general I sorta can't and shouldn't comment on the validity of rest of the case as a bystander. But when I read about that note in particular, my read on it was that somebody who actually did kill them versus somebody who just feels really bad about the situation and wants to vent in their own private space would write down the exact same thing in the exact same way with equivalent plausibility. She was a nurse, and babies died in her care; it is entirely plausible that, especially if she was already depressed, she would view that as being her fault and find some way to internalize the tragedy even if she didn't actually do anything to cause it. And, IIRC, Letby did basically say that that was what she meant by the note— So, in sum, an innocent person who had been blaming themselves and a murderer trying to lie their way out of justice IMO would have written down the exact same thing with equal plausibility, and then tried to explain it the exact same way, which means that IMO that datapoint is basically useless for determining her guilt. There was other evidence presented too, of course. I'm glad to hear that the conviction didn't rest on just that note, because given the situation, we don't actually know in isolation why she wrote that or what she meant by it— Most murderers try to avoid leaving confessions lying around to be used as evidence too.
  - ad404b8a372f2b9 3y ago
    And she had post-it notes at home where she had written "I killed them on purpose."...
  - littlestymaar 3y ago
    Like with the unauthorized interaction with the babies[1], this is only relevant to the case if (1) it's not a common behavior among nurses in her unit and (2) she did that specifically to the victims, and not with many of her patients. [1] https://news.ycombinator.com/item?id=37810382 https://news.ycombinator.com/item?id=37810382
- ssl232 3y ago
  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 https://twitter.com/profnfenton/status/1692837686166368660 [2] https://gill1109.com/2023/05/24/the-lucy-letby-case/ https://gill1109.com/2023/05/24/the-lucy-letby-case/ [3] https://twitter.com/LawHealthTech/status/1692917506078376019 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.
- littlestymaar 3y ago
  > that she was often caught interacting with those babies when she had been instructed not to This is only a piece of evidence if: - it's not a common behavior among nurses in her unit. - she did that specifically to the victims. Otherwise it could be that this rule isn't applied in practice, or that she is just the kind of people who don't really listen to instructions if they think they should not, which albeit a questionable attitude in an hospital isn't the same thing as “she killed them”.
- mrangle 3y ago
  Your second attempted point is nonsense in a working hospital setting in general, or in a courtroom as far as evidence is concerned. Your bookend points are the definition of particularly weak circumstantial evidence. Also known as statistical illusion. She should be in prison if guilty of these horrific crimes. However, sending an innocent person to prison for them is substantially worse than no one going to prison for them.
  - tbalsam 3y ago
    Every "innocent until proven guilty" still has a p value.
- taneq 3y ago
  I’ve watched enough cop procedurals to know that this means it was the ward manager. It’s too neat, obviously a set up. /s
- deleted 3y ago
  [deleted]
- YeGoblynQueenne 3y ago
  I made another post yesterday on the argument that "that the suspicious deaths all lined up perfectly with Lucy Letby's shifts": https://news.ycombinator.com/item?id=37814339 https://news.ycombinator.com/item?id=37814339 Those arguments, as presented to the jury, relied entirely on a spreadsheet of the nurses' duty roster. There's an image here (on the Daily Mail website): https://i.dailymail.co.uk/1s/2023/08/18/22/74487747-12286051-image-a-10_1692394380922.jpg https://i.dailymail.co.uk/1s/2023/08/18/22/74487747-12286051... Looking at this spreadsheet the one thing that immediately jumps out to me is that this spreadsheet is not the entire data. The spreadsheet shows only the days where Lucy Letby was on shift and there was a suspicious incident (i.e. when a baby died or collapsed). It is very difficult to believe that there were no shifts were incidents occurred and Lucy Letby was not on shift, or times Lucy Letby was on shift but no incident occurred. Obviously, without that data that is not included in the spreadsheet it is impossible to draw any conclusions about Lucy Letby's correlation with the incidents she was convicted of causing. That's pretty much what the RSS letter points out, that: it is far from straightforward to draw conclusions from suspicious clusters of deaths in a hospital setting – it is a statistical challenge to distinguish event clusters that arise from criminal acts from those that arise coincidentally from other factors, even if the data in question was collected with rigour. And the data in that spreadsheet was certainly not presented with any rigour. Rather, this spreadsheet is a textbook example of cherry-picking. It only shows the data that justifies the prosecutor's claim. I have no way to know whether this was done consciously, in order to mislead, or it was merely the result of poor understand of statistics by police officers and prosecutors. I'm inclined to believe the latter was the case. In any case, _if_ the jurors were convinced by that spreadsheet of Lucy Letby's guilt, to whatever extent (weighing it in view of other evidence), then they did so without having enough information.
  - gus_massa 3y ago
    > It is very difficult to believe that there were no shifts were incidents occurred and Lucy Letby was not on shift, or times Lucy Letby was on shift but no incident occurred. I agree. It's very strange that there was not at least one case when she was not there. Death are very clear, but it's easy to use different criteria to classify an weird case as suspicious. I'd expect more cluster of nurses. There are a few that work (almost?) in all the cases during the day, but the nights are more random. Some nurses appear only one. Which one had a full time job there and which where hired only a few times? There is a strange diagonal that starts at Child D - Nurse H. How did they sort the nurses? Alphabetically? By some internal HR number? [It may be an artifact, because people is too good detecting patterns like diagonals. I was generating a similar random grid a few years ago, and I saw too many patterns that I suspected the random generator was wrong. But it was just me overfitting the data.]
Marazan 3y ago
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.
- notahacker 3y ago
  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)
contravariant 3y ago
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 https://en.m.wikipedia.org/wiki/Lucia_de_Berk
- DanBC 3y ago
  The difference is that statistics were used in de Berk's prosecution, but were not used in Letby's prosecution.
  - contravariant 3y ago
    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.
  - YeGoblynQueenne 3y ago
    Woa, careful. That's not true. The staff duty roster was used by the prosecution to argue that Lucy Letby "the common denominator" in all the suspicious deaths: Chief among these was the duty roster spreadsheet showing staff shifts, through which the Crown Prosecution Service (CPS) was "able to show the jury that Letby was the one common denominator in the series of deaths and sudden collapses on the neonatal unit". https://theweek.com/law/lucy-letby-and-the-importance-of-understanding-statistics-in-the-nhs https://theweek.com/law/lucy-letby-and-the-importance-of-und... That is totally statistical information - even though it's, shall we say, lay statistics and not what you'd expect to see from a statistician.
- Freak_NL 3y ago
  Please; write 'Lucia de Berk', not 'Lucia de B'. She was exonerated in full, and has since indicated quite clearly that she wishes to be known under her full name, not the initialized suspect name.
crote 3y ago
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.
- mrangle 3y ago
  Better evidence is irrelevant to her jury trial if false evidence was included in the form of misrepresented stats. Because that's how trial by jury works. She would get a retrial, at minimum, if a judiciary body were to be convinced that the prosecution introduced false evidence.
  - crote 3y ago
    From what I understand, they did not even attempt to introduce misrepresented stats as evidence in the Latby case - it simply wasn't needed. All the other evidence was already enough to get her convicted, so having better evidence led to the statistics becoming irrelevant.
rgrieselhuber 3y ago
Also “experts warn” is argumentum ad verecundiam.
- munch117 3y ago
  What's the latin name for "argument by using fancy latin names for things that could just as easily have been said in English"?
- lolinder 3y ago
  No, the headline is just documenting what the experts are saying, it can't contain a fallacy because it doesn't contain an argument. It's the experts themselves who are making the argument, and they're not simply saying "trust us, we're statisticians".
avianlyric 3y ago
The other half of the equation is bias in the investigation. Often a poor understanding of statistics is used to start investigations, unfortunately those investigations are started with the premise that a particular person “is probably guilty”. Turns out that when medical investigations are performed looking for wrongdoing, they’re much more likely to find wrongdoing that if the investigation was performed simply to understand if correct policy and procedure are followed. As a consequence it’s very normal for deaths previously ruled “normal” to suddenly become “suspicious”. When people have studied these types of investigations, and has the evidence re-evaluated by unbiased investigators, the results are usually that nothing untoward occurred, or that deaths are better explained by systemic failures rather than the actions of specific individuals. There’s a good reason why we don’t let police go on fishing expeditions. Medical investigations, frequently initiated by untrained administrators, and performed by individuals within a hospital with no formal training in performing unbiased investigations, nor given enough to perform proper investigations, simply don’t hold up to the standards we would expect from a criminal investigation. None of this is to say that the Letby verdict is unsafe, but it wouldn’t be the first time a medical investigation with lots of evidence resulted in an awful miscarriage of justice.
mrangle 3y ago
No one forgets. 'We have to remember the jury" isn't a persuasive argument. Juries are no match for statistical misrepresentation. Even beyond stats, juries get it wrong constantly. Courts don't have staff math experts, including the judge. Were expert witness mathemeticians trial participants at any point? It may be premature to claim that there was a miscarriage of justice, but it may be similarly unwise to imply that there likely wasn't.
wolverine876 3y ago
Did the statisticians question Letby's verdict? They are talking about inquiries into other clusters of deaths.
YeGoblynQueenne 3y ago
According to the judge of the trial, most of the evidence was circumstantial [1]. I don't know which part of the evidence the judge considered circumstantial, and which not. The police have said that the duty roster spreadsheet shown to the jurors was an important piece of evidence used to convince the jurors [2]. The spreadsheet in question has been circulated in the media (I'm assuming, by the police) and it can be found in various places [3]. Looking at that spreadsheet there is something that immediately jumps out to me and that makes me think that at least that piece of "statistical" evidence was downright dodgy. I am curious to know if anyone else on HN sees the same thing. Here's a direct link to the image on the Mail website: https://i.dailymail.co.uk/1s/2023/08/18/22/74487747-12286051-image-a-10_1692394380922.jpg https://i.dailymail.co.uk/1s/2023/08/18/22/74487747-12286051... To be clear: I'm not trying to trap anyone, I'm just really curious to see what everyone else thinks _about this particular piece of evidence_. ____________ [1] https://www.bbc.co.uk/news/uk-england-merseyside-66823777 https://www.bbc.co.uk/news/uk-england-merseyside-66823777 Summing up at the end of her trial, judge Mr Justice Goss told the jury it was a case in which the prosecution "substantially, but not wholly" relied on circumstantial evidence. [2] https://theweek.com/law/lucy-letby-and-the-importance-of-understanding-statistics-in-the-nhs https://theweek.com/law/lucy-letby-and-the-importance-of-und... Chief among these was the duty roster spreadsheet showing staff shifts, through which the Crown Prosecution Service (CPS) was "able to show the jury that Letby was the one common denominator in the series of deaths and sudden collapses on the neonatal unit". [3] https://www.dailymail.co.uk/news/article-12286051/Lucy-Letby-eight-missed-chances-stop-killer-nurse-murdering-babies.html https://www.dailymail.co.uk/news/article-12286051/Lucy-Letby... See first image on top, titled: "Staff chart that shows Letby was present at every chilling incident".
leoh 3y ago
Thanks for the reminder! I no longer will hold the belief that OJ was guilty!

by rwmj 3y ago

iudqnolq 3y ago

edit: wrong, can't delete

deleted 3y ago
[deleted]

quietbritishjim 3y ago

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.

automatic6131 3y ago
And she took home documents from several of those patients, which she'd have no ordinary reason to have fished out of the trash.
- frou_dh 3y ago
  And the little old thing that she wrote "I killed them on purpose" on a post-it-note at her house.
  - ad404b8a372f2b9 3y ago
    Ah jinx!
  - kitd 3y ago
    Those notes had little effect in her conviction apparently, according to a criminal psychiatrist on BBC radio. It is behaviour typical of someone suffering depression, for which she was having treatment at the time.
    - adammarples 3y ago
      Writing "I killed them on purpose" is not typical behaviour of depressed people.
      - kitd 3y ago
        I'm going by the testimony of a psychiatrist who had been following the trial. Depression can apparently push people into a mental world where everything is at rock bottom and what gets written is just an expression of that.
      - Intralexical 3y ago
        Most depressed people don't have strings of deaths following them wherever they go. It is not unexpected of depressed people to blame themselves for bad things that happen around them, I think. …For multiple reasons, (1.) because you really do hate yourself that much, and might view those tragic events as also personal failures, and (2.) because for the suicidally depressed, it can be a way to manufacture a reason to believe why you deserve to be hated or physically injured. IIRC the insulin levels or something were rather suspicious, but in general I sorta can't and shouldn't comment on the validity of rest of the case as a bystander. But when I read about that note in particular, my read on it was that somebody who actually did kill them versus somebody who just feels really bad about the situation and wants to vent in their own private space would write down the exact same thing in the exact same way with equivalent plausibility. She was a nurse, and babies died in her care; it is entirely plausible that, especially if she was already depressed, she would view that as being her fault and find some way to internalize the tragedy even if she didn't actually do anything to cause it. And, IIRC, Letby did basically say that that was what she meant by the note— So, in sum, an innocent person who had been blaming themselves and a murderer trying to lie their way out of justice IMO would have written down the exact same thing with equal plausibility, and then tried to explain it the exact same way, which means that IMO that datapoint is basically useless for determining her guilt. There was other evidence presented too, of course. I'm glad to hear that the conviction didn't rest on just that note, because given the situation, we don't actually know in isolation why she wrote that or what she meant by it— Most murderers try to avoid leaving confessions lying around to be used as evidence too.
- ad404b8a372f2b9 3y ago
  And she had post-it notes at home where she had written "I killed them on purpose."...
- littlestymaar 3y ago
  Like with the unauthorized interaction with the babies[1], this is only relevant to the case if (1) it's not a common behavior among nurses in her unit and (2) she did that specifically to the victims, and not with many of her patients. [1] https://news.ycombinator.com/item?id=37810382 https://news.ycombinator.com/item?id=37810382
ssl232 3y ago
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 https://twitter.com/profnfenton/status/1692837686166368660 [2] https://gill1109.com/2023/05/24/the-lucy-letby-case/ https://gill1109.com/2023/05/24/the-lucy-letby-case/ [3] https://twitter.com/LawHealthTech/status/1692917506078376019 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.
littlestymaar 3y ago
> that she was often caught interacting with those babies when she had been instructed not to This is only a piece of evidence if: - it's not a common behavior among nurses in her unit. - she did that specifically to the victims. Otherwise it could be that this rule isn't applied in practice, or that she is just the kind of people who don't really listen to instructions if they think they should not, which albeit a questionable attitude in an hospital isn't the same thing as “she killed them”.
mrangle 3y ago
Your second attempted point is nonsense in a working hospital setting in general, or in a courtroom as far as evidence is concerned. Your bookend points are the definition of particularly weak circumstantial evidence. Also known as statistical illusion. She should be in prison if guilty of these horrific crimes. However, sending an innocent person to prison for them is substantially worse than no one going to prison for them.
- tbalsam 3y ago
  Every "innocent until proven guilty" still has a p value.
taneq 3y ago
I’ve watched enough cop procedurals to know that this means it was the ward manager. It’s too neat, obviously a set up. /s
deleted 3y ago
[deleted]
YeGoblynQueenne 3y ago
I made another post yesterday on the argument that "that the suspicious deaths all lined up perfectly with Lucy Letby's shifts": https://news.ycombinator.com/item?id=37814339 https://news.ycombinator.com/item?id=37814339 Those arguments, as presented to the jury, relied entirely on a spreadsheet of the nurses' duty roster. There's an image here (on the Daily Mail website): https://i.dailymail.co.uk/1s/2023/08/18/22/74487747-12286051-image-a-10_1692394380922.jpg https://i.dailymail.co.uk/1s/2023/08/18/22/74487747-12286051... Looking at this spreadsheet the one thing that immediately jumps out to me is that this spreadsheet is not the entire data. The spreadsheet shows only the days where Lucy Letby was on shift and there was a suspicious incident (i.e. when a baby died or collapsed). It is very difficult to believe that there were no shifts were incidents occurred and Lucy Letby was not on shift, or times Lucy Letby was on shift but no incident occurred. Obviously, without that data that is not included in the spreadsheet it is impossible to draw any conclusions about Lucy Letby's correlation with the incidents she was convicted of causing. That's pretty much what the RSS letter points out, that: it is far from straightforward to draw conclusions from suspicious clusters of deaths in a hospital setting – it is a statistical challenge to distinguish event clusters that arise from criminal acts from those that arise coincidentally from other factors, even if the data in question was collected with rigour. And the data in that spreadsheet was certainly not presented with any rigour. Rather, this spreadsheet is a textbook example of cherry-picking. It only shows the data that justifies the prosecutor's claim. I have no way to know whether this was done consciously, in order to mislead, or it was merely the result of poor understand of statistics by police officers and prosecutors. I'm inclined to believe the latter was the case. In any case, _if_ the jurors were convinced by that spreadsheet of Lucy Letby's guilt, to whatever extent (weighing it in view of other evidence), then they did so without having enough information.
- gus_massa 3y ago
  > It is very difficult to believe that there were no shifts were incidents occurred and Lucy Letby was not on shift, or times Lucy Letby was on shift but no incident occurred. I agree. It's very strange that there was not at least one case when she was not there. Death are very clear, but it's easy to use different criteria to classify an weird case as suspicious. I'd expect more cluster of nurses. There are a few that work (almost?) in all the cases during the day, but the nights are more random. Some nurses appear only one. Which one had a full time job there and which where hired only a few times? There is a strange diagonal that starts at Child D - Nurse H. How did they sort the nurses? Alphabetically? By some internal HR number? [It may be an artifact, because people is too good detecting patterns like diagonals. I was generating a similar random grid a few years ago, and I saw too many patterns that I suspected the random generator was wrong. But it was just me overfitting the data.]

Marazan 3y ago

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.

notahacker 3y ago
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)

contravariant 3y ago

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 https://en.m.wikipedia.org/wiki/Lucia_de_Berk

DanBC 3y ago
The difference is that statistics were used in de Berk's prosecution, but were not used in Letby's prosecution.
- contravariant 3y ago
  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.
- YeGoblynQueenne 3y ago
  Woa, careful. That's not true. The staff duty roster was used by the prosecution to argue that Lucy Letby "the common denominator" in all the suspicious deaths: Chief among these was the duty roster spreadsheet showing staff shifts, through which the Crown Prosecution Service (CPS) was "able to show the jury that Letby was the one common denominator in the series of deaths and sudden collapses on the neonatal unit". https://theweek.com/law/lucy-letby-and-the-importance-of-understanding-statistics-in-the-nhs https://theweek.com/law/lucy-letby-and-the-importance-of-und... That is totally statistical information - even though it's, shall we say, lay statistics and not what you'd expect to see from a statistician.
Freak_NL 3y ago
Please; write 'Lucia de Berk', not 'Lucia de B'. She was exonerated in full, and has since indicated quite clearly that she wishes to be known under her full name, not the initialized suspect name.

crote 3y ago

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.

mrangle 3y ago
Better evidence is irrelevant to her jury trial if false evidence was included in the form of misrepresented stats. Because that's how trial by jury works. She would get a retrial, at minimum, if a judiciary body were to be convinced that the prosecution introduced false evidence.
- crote 3y ago
  From what I understand, they did not even attempt to introduce misrepresented stats as evidence in the Latby case - it simply wasn't needed. All the other evidence was already enough to get her convicted, so having better evidence led to the statistics becoming irrelevant.

rgrieselhuber 3y ago

Also “experts warn” is argumentum ad verecundiam.

munch117 3y ago
What's the latin name for "argument by using fancy latin names for things that could just as easily have been said in English"?
lolinder 3y ago
No, the headline is just documenting what the experts are saying, it can't contain a fallacy because it doesn't contain an argument. It's the experts themselves who are making the argument, and they're not simply saying "trust us, we're statisticians".

avianlyric 3y ago

The other half of the equation is bias in the investigation. Often a poor understanding of statistics is used to start investigations, unfortunately those investigations are started with the premise that a particular person “is probably guilty”. Turns out that when medical investigations are performed looking for wrongdoing, they’re much more likely to find wrongdoing that if the investigation was performed simply to understand if correct policy and procedure are followed. As a consequence it’s very normal for deaths previously ruled “normal” to suddenly become “suspicious”. When people have studied these types of investigations, and has the evidence re-evaluated by unbiased investigators, the results are usually that nothing untoward occurred, or that deaths are better explained by systemic failures rather than the actions of specific individuals. There’s a good reason why we don’t let police go on fishing expeditions. Medical investigations, frequently initiated by untrained administrators, and performed by individuals within a hospital with no formal training in performing unbiased investigations, nor given enough to perform proper investigations, simply don’t hold up to the standards we would expect from a criminal investigation. None of this is to say that the Letby verdict is unsafe, but it wouldn’t be the first time a medical investigation with lots of evidence resulted in an awful miscarriage of justice.

mrangle 3y ago

No one forgets. 'We have to remember the jury" isn't a persuasive argument. Juries are no match for statistical misrepresentation. Even beyond stats, juries get it wrong constantly. Courts don't have staff math experts, including the judge. Were expert witness mathemeticians trial participants at any point? It may be premature to claim that there was a miscarriage of justice, but it may be similarly unwise to imply that there likely wasn't.

wolverine876 3y ago

Did the statisticians question Letby's verdict? They are talking about inquiries into other clusters of deaths.

YeGoblynQueenne 3y ago

According to the judge of the trial, most of the evidence was circumstantial [1]. I don't know which part of the evidence the judge considered circumstantial, and which not. The police have said that the duty roster spreadsheet shown to the jurors was an important piece of evidence used to convince the jurors [2]. The spreadsheet in question has been circulated in the media (I'm assuming, by the police) and it can be found in various places [3]. Looking at that spreadsheet there is something that immediately jumps out to me and that makes me think that at least that piece of "statistical" evidence was downright dodgy. I am curious to know if anyone else on HN sees the same thing. Here's a direct link to the image on the Mail website: https://i.dailymail.co.uk/1s/2023/08/18/22/74487747-12286051-image-a-10_1692394380922.jpg https://i.dailymail.co.uk/1s/2023/08/18/22/74487747-12286051... To be clear: I'm not trying to trap anyone, I'm just really curious to see what everyone else thinks _about this particular piece of evidence_. ____________ [1] https://www.bbc.co.uk/news/uk-england-merseyside-66823777 https://www.bbc.co.uk/news/uk-england-merseyside-66823777 Summing up at the end of her trial, judge Mr Justice Goss told the jury it was a case in which the prosecution "substantially, but not wholly" relied on circumstantial evidence. [2] https://theweek.com/law/lucy-letby-and-the-importance-of-understanding-statistics-in-the-nhs https://theweek.com/law/lucy-letby-and-the-importance-of-und... Chief among these was the duty roster spreadsheet showing staff shifts, through which the Crown Prosecution Service (CPS) was "able to show the jury that Letby was the one common denominator in the series of deaths and sudden collapses on the neonatal unit". [3] https://www.dailymail.co.uk/news/article-12286051/Lucy-Letby-eight-missed-chances-stop-killer-nurse-murdering-babies.html https://www.dailymail.co.uk/news/article-12286051/Lucy-Letby... See first image on top, titled: "Staff chart that shows Letby was present at every chilling incident".

leoh 3y ago

Thanks for the reminder! I no longer will hold the belief that OJ was guilty!