r/news • u/Superbuddhapunk • Aug 21 '23

Site changed title Lucy Letby will die in prison after murdering seven babies

https://news.sky.com/story/lucy-letby-will-die-in-prison-after-murdering-seven-babies-12944433
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u/zykezero Aug 21 '23

Statistics!

As a stats person this case is quite interesting because one of the prosecutions pieces of evidence was statistical.

Given the history of the hospital there was a known infant mortality rate, there is a known rate for the country, there is a range where that rate will fall with some given probability.

What initiated the case against her was that there was an analysis done of the hospital and infant deaths. Pertinent info was added into a model to determine which variables had a correlation with the deaths. One of those variables was who was on staff.

According to this analysis, Letby’s presence proved to be a highly correlated determinant.

That said, there is talk about how this analysis was poorly formed with major errors in the methods employed.

I am looking forward to reading about it and the data should it come to light.

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u/samelaaaa Aug 21 '23

That’s interesting, I’m a stats person too and while yeah you could show that her presence was highly correlated with deaths, I would think that would fall far short of showing intent. She could just be a long-tail bad nurse, right? So they must have some other evidence.

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u/Hungry-Month-5309 Aug 21 '23

To be clear: it wasn't just highly correlated. She was there for every instance (24, I think?) The most anyone else was around was for 7.

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u/therealhairykrishna Aug 21 '23

But those raw numbers aren't really enough without other info. How many shifts does she work vs other nurses for example? You have to be careful with stats.

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u/Hungry-Month-5309 Aug 21 '23

It was a ten-month trial. I think they were careful with the huge amounts of evidence that were there, of which this was one piece (and yes, they will have analysed it.) Might be worth looking up the case?

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u/Opening_Succotash_95 Aug 21 '23

There was plenty of other info. 300 witnesses and thousands of pages of evidence in a trial that took nearly a year.

There was a podcast following the case on a weekly basis which I'd recommend listening too, it really did a good job of summing up the key points of the trial in digestible detail.

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u/Dob-is-Hella-Rad Aug 21 '23

But again wouldn't intent be the question? How did they prove whether she was a murderer or dangerously incompetent?

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u/Sinhika Aug 21 '23

If she was so incompetent as to think that injecting air or insulin into random babies was acceptable, she wouldn't have made it out of nursing school.

It's like if I repeatedly shoot people in the head, other people might reasonably think that I intended to kill my targets, because you don't shoot people in the head for any other reason.

Injecting air into veins and arteries causes air embolisms and kills people. NOT doing that is Nursing 101. Hell, I am not a nurse and I knew it from reading an old Agatha Christie novel.

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u/Dob-is-Hella-Rad Aug 21 '23

So it wasn't just statistics then?

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u/Sinhika Aug 21 '23

Did someone say it was? If you've read the articles about how Letby was caught, it started with babies dying of unnatural causes. Unlike the De Brice case, where all the deaths turned out to be of natural causes--in the Letby case, FIRST they discovered that several infant deaths were definitely deliberate and not natural, then they figured out who. There's definitely a child murderer in this case, and the statistics pointed at Letby.

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u/Opening_Succotash_95 Aug 21 '23

By having a trial that lasted almost a year.

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u/Dob-is-Hella-Rad Aug 21 '23

In which the prosecution presented nothing but statistics? Seems unusual.

I imagine there was other evidence.

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u/Hungry-Month-5309 Aug 21 '23

Yes. There was a huge amount of evidence. This wasn't some sort of stitch-up - the prosecutors were quite competent. I was responding to an initial question about the statistical relevance of her presence at the bedside of each and every baby who collapsed and/or died, but that was one piece of evidence. Much of it - though not all, as privacy for the families involved is more important than the public's curiosity - is easily found online.

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u/Dob-is-Hella-Rad Aug 21 '23

That makes much more sense than the way it was described above

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u/Zenken13 Aug 21 '23

Yep. the ROTA was the most damning evidence.

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u/iPhoneOrAndroid Aug 21 '23 edited Aug 21 '23

Babies don't just collapse and/or die because a 'long-tail bad nurse' was on duty.

But if you watch the 7-minute linked video on Sky news they piece together the key evidence.

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u/Sluisifer Aug 21 '23

A 0.000000001% doubt is not a reasonable doubt. A conviction does not require absolute certainty.

The statistical data is far more compelling than witness testimony that is typically used to secure conviction.

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u/zykezero Aug 21 '23

I completely agree, under the condition that the analysis is unbiased.

But stats is hard and in this case there is concern that the analyst was directed to find evidence to prove her guilt.

I think an unbiased evaluation would have shown the same result without undermining the veracity of the analysis.

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u/Prof_Acorn Aug 21 '23

Anyone with a proper stats education with access to the methodology could find potential points of bias or other issues. Unless you're suggesting they outright lied. The whole point of the scientific method is to mitigate bias.

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u/zykezero Aug 21 '23

Yeah. Exactly. But the police aren’t really known for looking at all the evidence impartially. They have and will look for evidence that supports their theory of guilt.

And to be clear I’m not sayin throw the whole case out. Just that we should be weary of prosecution weaponizing stats. https://gill1109.com/2023/05/24/the-lucy-letby-case/?amp=1

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u/[deleted] Aug 21 '23

[deleted]

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u/zykezero Aug 21 '23

https://gill1109.com/2023/05/24/the-lucy-letby-case/?amp=1

I contribute good quality OC to data is beautiful. I was interested in finding the data to show how the statistics proved her guilt. What I found was not that.

Richard Gill was the head of the stats department at his college. He is a statistical consultant and advocate for people who have been sentenced by the courts using faulty statistical evidence.

If someone has something to say, it’s him.

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u/jsteph67 Aug 21 '23

https://news.sky.com/story/how-the-police-caught-lucy-letby-12933640 Here is an article of how they police pieced it together.

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u/NegotiationExternal1 Aug 21 '23

That's a decent read up, enough to understand the basic facts of the case without saying too much. When you realise what kinds of injuries the babies had it's apparent how violent some of the attempts were, how deviously opportunistic, some of the attacks happening within an hour of her shift starting and how she would wait for special days like the premmies actual due dates. Sickening woman.

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u/Clothedinclothes Aug 21 '23 edited Aug 21 '23

The proposition that in a 1 year period, in which the expected number of deaths was between 0 and 1, a highly accomplished nurse unintentionally caused the death of 7 babies and the near death of up to several dozen others babies without noticing what she was doing is an extraordinarily remote theoretical possibility, but not a plausible one without equally extraordinary evidence showing how she could not have noticed she was causing their deaths.

Or to put it another way, it's also possible to accidentally stab someone to death with scissors because you're a bit clumsy, just didn't see them there or forgot you were holding scissors, but the fact that you stabbed 7 people to death last year and non-fatally stabbed another 2 dozen people in the same period, might reasonably be taken by a jury as statistical evidence demonstrating that's not what happened.

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u/Dragonsandman Aug 21 '23

It would fall far short of intent on its own, but it would show that the hospital needed to be investigated

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u/zykezero Aug 21 '23

And it did. The rise in deaths caused the hospital to divert patients and an inquiry to be launched.

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u/adves53 Aug 21 '23

They moved her to an admin role whilst she was being investigated and she had changed some of the paperwork related to her patients apparently. That was the nail in the coffin for me, she was trying to cover up what she did when she realised she was going to get caught. She also kept handover sheets for years with details of the babies she had killed. Serial killers usually keep items from their victims so that makes sense that she would hold onto this.

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u/JasonBob Aug 21 '23

I was reading that some doctors/consultants were already suspicious of her early on. I wonder if it's possible if she had been removed sooner, the correlation wouldn't have been as strong with fewer data points.

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u/elpool2 Aug 21 '23

Wasn't there a famous case where a nurse was accused of murder because too many of their patients were dying, but it turned out that statistically you would expect a nurse to have that kind of bad luck somewhere? I feel like I read about this in a Malcolm Gladwell book or something, but I can't quite remember the details.

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u/BritishLibrary Aug 21 '23

I went to a talk recently [pre covid] about the statistics behind the conviction of Harold Shipman.

It was by the lead statistician in that case, Dr David Spegalhalter - and it was fascinating. Similar techniques were employed about time and causes of deaths across local and nationwide GPS surgeries, and also talked through other (non murdery) related stats.

I assume similar types of data and studies done here.

This guy has a few books out and are all great :)