7 ms·

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

piker 3y ago
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?
- anewhnaccount2 3y ago
  The evidence suggests that many of the deaths had symptoms consistent with being injected with air. We would need to have a model of P(symptoms_i|not injected with air) to try and get to the possibility of there having been a miscarriage of justice.
- DanBC 3y ago
  > 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.
  - d1sxeyes 3y ago
    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”.
- randomcarbloke 3y ago
  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.
  - pbhjpbhj 3y ago
    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.
- krisoft 3y ago
  There were various postmortem findings described as anomalous. Child F had a bloodwork which indicated that someone gave them a large amount of insulin. Child D’s post mortem X-ray is said to show air injected into their blood vessels. Child L also had insulin in their blood. I’m not an expert so I can’t say for certain how strong these evidence are. Also my understanding that while these are evidence that a crime happened, they do not tie Lucy directly to the crime. The evidence for that is circumstatial, mainly that she was the only one on duty for all the collapses said to be suspicious.
  - YeGoblynQueenne 3y ago
    >> Child F had a bloodwork which indicated that someone gave them a large amount of insulin. >> Child L also had insulin in their blood. Those were not post-mortems because these two children didn't die. Lucy Letby was accused of attempting to murder them, by injecting them with insulin. See here, towards the end of the article, a summary of accusations and convictions: https://www.nursingtimes.net/news/children/breaking-lucy-letby-convicted-of-murdering-seven-babies-at-hospital-neonatal-unit-18-08-2023/ https://www.nursingtimes.net/news/children/breaking-lucy-let...
    - krisoft 3y ago
      You are correct. Thank you for the correction.
- crote 3y ago
  I recommend reading the Wikipedia page, the "2023 Trial" section has a pretty good overview.
orra 3y ago
Quite right. I remember Ben Goldacre's book Bad Science documenting a few examples. I hope these are the same examples raised in the letter, because otherwise a lot of miscarriage of justice has happened in the UK. What I remember from the book is entirely innocent people jailed because the wrong statistical question was asked. IIRC along the lines of two deaths, and the question asked was what is the chance of this happening? As opposed to, assuming the first death, what is the chance of the second? As opposed to, assuming two deaths, what is the chance of bad luck versus malice. (I am not commenting on the Letby case per se. AIUI there is an appeal pending and UK law can be rather strict. Simply, we should not respond to possible horrible events by convicting other people who are innocent of statistical flukes, or misrepresented statistics.)
- DanBC 3y ago
  Just for clarity: statistics were not used in the Letby prosecution. The problem with Letby is that a serial killer was able to hide because finding a rare event (a member of staff murdering multiple babies) is hard to do in the noise (the mish mash of data available). Currently the English NHS is moving away from SIRI (Serious Incident Requiring Investigation) to PSIRF (Patient Safety Incident Response Framework) which focuses a lot more on "no blame" and "open culture", so it's important that NHS Trusts get the stats right to be able to detect and understand these very rare events.
  - YeGoblynQueenne 3y ago
    >> Just for clarity: statistics were not used in the Letby prosecution. I was going to say that this is the second time I see someone in this thread claim this, but I noticed the other comment is also from your account: https://news.ycombinator.com/item?id=37814660 https://news.ycombinator.com/item?id=37814660 As I say in that other comment, statistics were used in Lucy Letby's trial, in the form of the staff duty roster spreadsheet that the prosecution showed to the jurors to convince them that Lucy Letby was a "common denominator" in all the suspicious incidents.
- InCityDreams 3y ago
  >otherwise a lot of miscarriage of justice has happened in the UK. Depends on 'a lot', but I rather suspect there will be/ will have been fewer, now cops have to use cameras, but yes - a lot of miscarriages of justice has happened in the UK. And every other country.
brvsft 3y ago
> 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-police-found-note-saying-i-killed-them-on-purpose-court-hears 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 capital letters: “I AM EVIL I DID THIS,” the jury was told. > She also wrote on the note: “There are no words”, “I can’t breathe”, “kill myself”, “I haven’t done anything wrong”, “how can I get through it?” and “I am an awful person”. She had also written “No Hope” and “Panic Fear” and then circled in capital letters “HATE”. Personally, I don't think any of this is strong evidence, since she contradicts herself a bit. But the notes more directly address the murders because she wrote them in response to the accusations. It isn't as vague as a diary entry mentioning a secret. And as far as I know, they had more evidence in the form of testimony from experts suggesting the babies were killed by injecting them with air, but I'm sure there are reasons to be skeptical of that. Mainly, I don't know how strongly any statistical "evidence" was presented in court, how much the jury depended on it in their guilty verdict, and how the UK court system works, so I don't have a strong opinion. But I also don't believe a not-guilty person would think to write anything like what she wrote in those notes. One last thing I'm curious about and have never heard definitive information on is whether babies stopped dying when they took Letby out of the NICU or whatever they call it. I suppose that might still be accounted for in this statistical coincidence element the RSS and other statisticians are discussing.
- specialist 3y ago
  [deletia, cuz I misread the article.]
  - kitd 3y ago
    No it wasn't. See my sibling comment in this thread. At worst, it alerted authorities to there potentially being foul play. Her actual conviction was based on other factors.
JackeJR 3y ago
The expert statistical analysis alluded to is simply the framework for causal inference. Had Letby not been on duty for a similar group of patients, would the number of patients who had died been the same? If the answer is no, then a follow on question regarding whether or not factors associated with Letby could have resulted in the deaths rather than Letby herself. This could be a fellow worker who always worked in tandem with her etc. Finding the appropriate set of data and applying statistical techniques for this is not trivial hence the expert mention.
oxfordmale 3y ago
In two cases, the victim died by insulin overdose, Letby herself admitted that the only possible explanation was foul play. That means there is a killer on the ward. The police interviewed the other nurse on the shift, and she was cleared. Even if Letby gets acquitted from the other cases, her sentencing likely will not change. One challenge for the defence was that there are few studies on injecting air in small babies for obvious reasons. Air embolisms are very painful, and such a study wouldn't pass ethics approval, let alone parental consent.
- YeGoblynQueenne 3y ago
  Those babies didn't die. Those were not murder accusations but attempted murder. To clarify. Lucy Letby was accused of deliberately administering a high dose of insulin to two babies, in an attempt to murder them. Those two babies were "Child F", and "Child L" for both of which she was charged , and convicted of attempted murder. My source for this information is this article in "Nursing Times": https://www.nursingtimes.net/news/children/breaking-lucy-letby-convicted-of-murdering-seven-babies-at-hospital-neonatal-unit-18-08-2023/ https://www.nursingtimes.net/news/children/breaking-lucy-let...
  - oxfordmale 3y ago
    Thanks for correcting this mistake. My point is that the judge awarded her a life sentence on each of the cases: "on each of the seven offences of murder, and the seven offences of attempted murder, I sentence you to imprisonment for life." Even if the other cases turn out to be unsafe, she would still be imprisoned for life.
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!
mberning 3y ago
I think this is a great example of a justice system working as intended. The statistical evidence alone likely would not have convicted her, but it could have exonerated or cast doubt on her being the perpetrator. It did not, for reasons which were obvious to the jury.
mellosouls 3y ago
There seems to be some (understandable) confusion in some of the comments about what the article here is reporting which isn't helped by a lack of clarity in it or the underlying Guardian piece, possibly in each case intended to push their own agendas. There appears to be an interpretation here by some of a potentially unsafe verdict due to misreading of statistics in her conviction - which has certainly happened in the past in other cases including those mentioned. The expert input here though is intended as advice for the inquiry into what went wrong at the places Letby worked to lessen the risk of it happening again. That necessarily includes qualified and responsible analyses of statistics, which will also have the benefit of increasing protection and support of staff as well as improving safety generally.
zee2345 3y ago
[flagged]
fiftyacorn 3y ago
One thing the Letby trial left me wondering was how do doctors and nurses working in areas with higher levels of mortality protect themselves from this sort of accusation? And whether this would put doctors off doing riskier procedures?
- jdietrich 3y ago
  The suspicious deaths in this case were systematically ignored by hospital management. Doctors who raised concerns about Letby were disciplined for doing so. The hospital is now under police investigation on suspicion of corporate manslaughter, because it is highly likely that deaths could have been prevented if they had investigated rather than silenced those concerns. https://www.bbc.co.uk/news/uk-66120934 https://www.bbc.co.uk/news/uk-66120934 https://www.bbc.co.uk/news/uk-england-merseyside-67006930 https://www.bbc.co.uk/news/uk-england-merseyside-67006930
Xenoamorphous 3y ago
Kathleen Folbig case might me related to what it’s being discussed. She had four children die shortly after being born and she was sent to jail.
hmottestad 3y ago
I like to remember that the odds of winning the lottery are easily in the 1 in 50 million, yet people still seem to win it. It’s statistically improbably to get 7 sons, but I’m certain that throughout history that’s happened at least once.
- sgt101 3y ago
  it's only statistically improbable to get 7 sons (in a row) if you have all couples that create 7 children have a 50/50 chance of son/daughter. If you have a reason why a couple will only produce sons (genetics) then it becomes much less surprising.
- Huggernaut 3y ago
  At my primary school there were twin boys, with 3 older brothers, 1 younger and no other siblings so they were damn close!
rossant 3y ago
Not directly related to this case, but the book Math on trial by Leila Schneps and Coralie Colmez covers several examples of misapplied statistics in court: https://en.m.wikipedia.org/wiki/Math_on_Trial https://en.m.wikipedia.org/wiki/Math_on_Trial

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?

anewhnaccount2 3y ago
The evidence suggests that many of the deaths had symptoms consistent with being injected with air. We would need to have a model of P(symptoms_i|not injected with air) to try and get to the possibility of there having been a miscarriage of justice.
DanBC 3y ago
> 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.
- d1sxeyes 3y ago
  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”.
randomcarbloke 3y ago
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.
- pbhjpbhj 3y ago
  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.
krisoft 3y ago
There were various postmortem findings described as anomalous. Child F had a bloodwork which indicated that someone gave them a large amount of insulin. Child D’s post mortem X-ray is said to show air injected into their blood vessels. Child L also had insulin in their blood. I’m not an expert so I can’t say for certain how strong these evidence are. Also my understanding that while these are evidence that a crime happened, they do not tie Lucy directly to the crime. The evidence for that is circumstatial, mainly that she was the only one on duty for all the collapses said to be suspicious.
- YeGoblynQueenne 3y ago
  >> Child F had a bloodwork which indicated that someone gave them a large amount of insulin. >> Child L also had insulin in their blood. Those were not post-mortems because these two children didn't die. Lucy Letby was accused of attempting to murder them, by injecting them with insulin. See here, towards the end of the article, a summary of accusations and convictions: https://www.nursingtimes.net/news/children/breaking-lucy-letby-convicted-of-murdering-seven-babies-at-hospital-neonatal-unit-18-08-2023/ https://www.nursingtimes.net/news/children/breaking-lucy-let...
  - krisoft 3y ago
    You are correct. Thank you for the correction.
crote 3y ago
I recommend reading the Wikipedia page, the "2023 Trial" section has a pretty good overview.

orra 3y ago

Quite right. I remember Ben Goldacre's book Bad Science documenting a few examples. I hope these are the same examples raised in the letter, because otherwise a lot of miscarriage of justice has happened in the UK. What I remember from the book is entirely innocent people jailed because the wrong statistical question was asked. IIRC along the lines of two deaths, and the question asked was what is the chance of this happening? As opposed to, assuming the first death, what is the chance of the second? As opposed to, assuming two deaths, what is the chance of bad luck versus malice. (I am not commenting on the Letby case per se. AIUI there is an appeal pending and UK law can be rather strict. Simply, we should not respond to possible horrible events by convicting other people who are innocent of statistical flukes, or misrepresented statistics.)

DanBC 3y ago
Just for clarity: statistics were not used in the Letby prosecution. The problem with Letby is that a serial killer was able to hide because finding a rare event (a member of staff murdering multiple babies) is hard to do in the noise (the mish mash of data available). Currently the English NHS is moving away from SIRI (Serious Incident Requiring Investigation) to PSIRF (Patient Safety Incident Response Framework) which focuses a lot more on "no blame" and "open culture", so it's important that NHS Trusts get the stats right to be able to detect and understand these very rare events.
- YeGoblynQueenne 3y ago
  >> Just for clarity: statistics were not used in the Letby prosecution. I was going to say that this is the second time I see someone in this thread claim this, but I noticed the other comment is also from your account: https://news.ycombinator.com/item?id=37814660 https://news.ycombinator.com/item?id=37814660 As I say in that other comment, statistics were used in Lucy Letby's trial, in the form of the staff duty roster spreadsheet that the prosecution showed to the jurors to convince them that Lucy Letby was a "common denominator" in all the suspicious incidents.
InCityDreams 3y ago
>otherwise a lot of miscarriage of justice has happened in the UK. Depends on 'a lot', but I rather suspect there will be/ will have been fewer, now cops have to use cameras, but yes - a lot of miscarriages of justice has happened in the UK. And every other country.

brvsft 3y ago

> 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-police-found-note-saying-i-killed-them-on-purpose-court-hears 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 capital letters: “I AM EVIL I DID THIS,” the jury was told. > She also wrote on the note: “There are no words”, “I can’t breathe”, “kill myself”, “I haven’t done anything wrong”, “how can I get through it?” and “I am an awful person”. She had also written “No Hope” and “Panic Fear” and then circled in capital letters “HATE”. Personally, I don't think any of this is strong evidence, since she contradicts herself a bit. But the notes more directly address the murders because she wrote them in response to the accusations. It isn't as vague as a diary entry mentioning a secret. And as far as I know, they had more evidence in the form of testimony from experts suggesting the babies were killed by injecting them with air, but I'm sure there are reasons to be skeptical of that. Mainly, I don't know how strongly any statistical "evidence" was presented in court, how much the jury depended on it in their guilty verdict, and how the UK court system works, so I don't have a strong opinion. But I also don't believe a not-guilty person would think to write anything like what she wrote in those notes. One last thing I'm curious about and have never heard definitive information on is whether babies stopped dying when they took Letby out of the NICU or whatever they call it. I suppose that might still be accounted for in this statistical coincidence element the RSS and other statisticians are discussing.

specialist 3y ago
[deletia, cuz I misread the article.]
- kitd 3y ago
  No it wasn't. See my sibling comment in this thread. At worst, it alerted authorities to there potentially being foul play. Her actual conviction was based on other factors.

JackeJR 3y ago

The expert statistical analysis alluded to is simply the framework for causal inference. Had Letby not been on duty for a similar group of patients, would the number of patients who had died been the same? If the answer is no, then a follow on question regarding whether or not factors associated with Letby could have resulted in the deaths rather than Letby herself. This could be a fellow worker who always worked in tandem with her etc. Finding the appropriate set of data and applying statistical techniques for this is not trivial hence the expert mention.

oxfordmale 3y ago

In two cases, the victim died by insulin overdose, Letby herself admitted that the only possible explanation was foul play. That means there is a killer on the ward. The police interviewed the other nurse on the shift, and she was cleared. Even if Letby gets acquitted from the other cases, her sentencing likely will not change. One challenge for the defence was that there are few studies on injecting air in small babies for obvious reasons. Air embolisms are very painful, and such a study wouldn't pass ethics approval, let alone parental consent.

YeGoblynQueenne 3y ago
Those babies didn't die. Those were not murder accusations but attempted murder. To clarify. Lucy Letby was accused of deliberately administering a high dose of insulin to two babies, in an attempt to murder them. Those two babies were "Child F", and "Child L" for both of which she was charged , and convicted of attempted murder. My source for this information is this article in "Nursing Times": https://www.nursingtimes.net/news/children/breaking-lucy-letby-convicted-of-murdering-seven-babies-at-hospital-neonatal-unit-18-08-2023/ https://www.nursingtimes.net/news/children/breaking-lucy-let...
- oxfordmale 3y ago
  Thanks for correcting this mistake. My point is that the judge awarded her a life sentence on each of the cases: "on each of the seven offences of murder, and the seven offences of attempted murder, I sentence you to imprisonment for life." Even if the other cases turn out to be unsafe, she would still be imprisoned for life.

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!

mberning 3y ago

I think this is a great example of a justice system working as intended. The statistical evidence alone likely would not have convicted her, but it could have exonerated or cast doubt on her being the perpetrator. It did not, for reasons which were obvious to the jury.

mellosouls 3y ago

There seems to be some (understandable) confusion in some of the comments about what the article here is reporting which isn't helped by a lack of clarity in it or the underlying Guardian piece, possibly in each case intended to push their own agendas. There appears to be an interpretation here by some of a potentially unsafe verdict due to misreading of statistics in her conviction - which has certainly happened in the past in other cases including those mentioned. The expert input here though is intended as advice for the inquiry into what went wrong at the places Letby worked to lessen the risk of it happening again. That necessarily includes qualified and responsible analyses of statistics, which will also have the benefit of increasing protection and support of staff as well as improving safety generally.

zee2345 3y ago

[flagged]

fiftyacorn 3y ago

One thing the Letby trial left me wondering was how do doctors and nurses working in areas with higher levels of mortality protect themselves from this sort of accusation? And whether this would put doctors off doing riskier procedures?

jdietrich 3y ago
The suspicious deaths in this case were systematically ignored by hospital management. Doctors who raised concerns about Letby were disciplined for doing so. The hospital is now under police investigation on suspicion of corporate manslaughter, because it is highly likely that deaths could have been prevented if they had investigated rather than silenced those concerns. https://www.bbc.co.uk/news/uk-66120934 https://www.bbc.co.uk/news/uk-66120934 https://www.bbc.co.uk/news/uk-england-merseyside-67006930 https://www.bbc.co.uk/news/uk-england-merseyside-67006930

Xenoamorphous 3y ago

Kathleen Folbig case might me related to what it’s being discussed. She had four children die shortly after being born and she was sent to jail.

hmottestad 3y ago

I like to remember that the odds of winning the lottery are easily in the 1 in 50 million, yet people still seem to win it. It’s statistically improbably to get 7 sons, but I’m certain that throughout history that’s happened at least once.

sgt101 3y ago
it's only statistically improbable to get 7 sons (in a row) if you have all couples that create 7 children have a 50/50 chance of son/daughter. If you have a reason why a couple will only produce sons (genetics) then it becomes much less surprising.
Huggernaut 3y ago
At my primary school there were twin boys, with 3 older brothers, 1 younger and no other siblings so they were damn close!

rossant 3y ago

Not directly related to this case, but the book Math on trial by Leila Schneps and Coralie Colmez covers several examples of misapplied statistics in court: https://en.m.wikipedia.org/wiki/Math_on_Trial https://en.m.wikipedia.org/wiki/Math_on_Trial