Kathleen Folbigg, angela cannings, Sally Clark

Lucia de Berk: A Dutch nurse who was wrongly convicted of murdering several patients. Her conviction was eventually overturned after it was determined that statistical errors and misinterpretation of medical evidence led to her wrongful conviction.

Susan Nelles: A Canadian nurse accused of murdering babies in her care. She was charged but later acquitted due to lack of evidence.

Daniela Poggiali: An Italian nurse accused of murdering patients in a hospital. She was initially convicted but later acquitted on appeal due to lack of conclusive evidence.

Jane Bolding: A British nurse accused of murdering patients in her care. She was acquitted after a retrial due to lack of evidence.

Ben Geen: A British nurse convicted of murdering patients by inducing hypoglycemia. His conviction was quashed after it was determined that evidence presented against him was unreliable.

Colin Norris: A British nurse convicted of murdering patients by injecting insulin. His conviction was quashed after it was determined that there were serious flaws in the medical evidence and prosecution case.

Alleged Method

  • Potassium Chloride: easily available, easy to administer, kills quickly, quickly dissipates and is hard to detect.

Resources

Caption text
Category Daniela Poggiali Lucia de Berk Jane Bolding Lucy Letby
“Incriminating” evidence
  • Took selfies laughing with dead body
  • She had the ability to switch between wings of hospital
  • Fiery temper, played pranks on colleagues
  • Found patients irritating
  • Allegations of thefts of jewellery
Example Example
  • Googled parents
  • That post-it note
  • The increased insulin without corresponding C-peptide in 2 victims
  • Had lots of teddy bears
Motive “She must have just loved killing people” Example Example Example
Actual evidence Correlation between shifts and deaths Example Example Correlation between shifts and deaths
Mitigants
  • Large ward many patients
  • High proportion of very old and terminally ill patients
  • Data collection was pretty ropey
Example Example Example
Alleged Method Pottassium Choloride Example Example Several
Resources Richard Gill blog Example Example New Yorker article

We need to talk about lucy letby podcast

Peasant 2:

Peasant 1: We have found a witch may we burn her?
Peasant 2: Burn her!
Bedevere: How do you know she is a witch?
Peasant 1: She looks like one
Bedevere: Bring her forward.
Woman: I am not a witch
Bedevere:But you are dressed as one
Woman: They dressed me up like this
Peasant 1: We didn't!
Woman: And this isn't my nose it's a false one
Bedevere:Well?
Peasant 1: Well, we did do the nose
Bedevere: The nose?
Peasant 2: And the hat but she is a witch
Peasant 1: Burn her!
Bedevere: Did you dress her up like this?
Peasant 1: No.
Peasant 2: Yes.
Peasant 3: Yes.
Peasant 3: A bit. She has got a wart.
Bedevere: What makes you think she is a witch?
Peasant 1: Well, she turned me into a newt.
Bedevere: A newt?
Peasant 1: I got better.
Peasant 2: Burn her anyway!
Peasant 1: Burn her!
Bedevere: Quiet! There are ways of telling whether she is a witch.
Peasant 1: Are there? What are they? Tell us.
Bedevere: Tell me, what do you do with witches?
Peasant 1: Burn them!
Bedevere: What do you burn apart from witches?
Peasant 1: More witches!
Peasant 2: Wood.
Bedevere: So, why do witches burn?
Peasant 1: Because they're made of wood?
Bedevere: Good!
Bedevere: So, how do we tell whether she is made of wood?
Peasant 1: Build a bridge out of her!
Bedevere: Can you not also make bridges of stone?
Peasant 1: Oh, yeah.
Bedevere: Does wood sink in water?
Peasant 1: No. It floats! Throw her into the pond!
Bedevere: What also floats in water?
Peasant 1: Bread.
Peasant 2: Apples.
Peasant 3: Very small rocks.
Peasant 4: Cider.
Peasant 5: Cherries.
Peasant 6: Gravy.
Peasant 7: Mud.
Peasant 8: Churches.
Peasant 9: Lead.
Arthur: A duck!
Bedevere: Exactly. So, logically —
Peasant 1: If she weighs the same as a duck, she's made of wood.
Bedevere: And, therefore?


Peasant 1: A witch!
Peasant 1: A witch!

Holmes

JHB: what could have been the tell-tale signs that this woman was a danger? Was there anything that could have given us forewarning? Holmes: “Well, it may not give forewarning but generally speaking, [with] a serial killer of this stature really it’s almost obligatory to have psychopathic traits and they will often show themselves in various ways. ... she was very controlled. She was trying to give the image of a very responsible, caring nurse who would be there in a crisis to save babies and so on and so forth. So she is playing the role of someone who would not be suspected other than the correlation between her and the babies’ deaths.”

“It’s a situation where you have not got any really concrete evidence: one piece, like a CCTV camera footage or a witness, etc, all you’ve got is an accumulation of basically very low-level evidence — coincidences, etc — but when you actually accumulate a large number of these [using] something called a Bayesian analysis, it’s actually more statistically sound to have 100 little arrows pointing towards Lucy and none pointing away from her, and I think that’s how justice was actually reached.”

—Criminologist David Holmes on Sky News, 18 August 2023

Well, to a point. Bayesian analysis starts with a “prior probability” — an initial estimate of the likelihood that “Lucy Letby murdered multiple neonatal infants with no motive, no psychiatric history and no prior tendency” — which is extremely low — and adjusts it to a “posterior probability” on the cumulative effect of the “little arrows” to revise the likelihood of it being true. An accumulation of even weak “little arrows” can increase the “posterior” probability of the hypothesis, but if all the arrows are also consistent with another explanation, their contribution to updating a Bayesian analysis may be modest. There is significant potential for false positives when dealing with rare events and weak evidence. (Compare this with David Bain’s case, where the prior probability that he was the culprit was already high (the event was certainly murder, and he was one of only two plausible suspects), and the circumstantial evidence against him was strong, and Lindy Chamberlain, where the prior probability was very low, and the circumstantial evidence weak).

Prior and posterior probabilities in different cases
Case There was a Murder Suspect responsible Another person responsible
Prior Posterior Prior Posterior Prior Posterior
OJ Simpson Certain Unchanged Very likely Greatly increased Fairly unlikely Unchanged
David Bain Certain Unchanged Fairly likely Greatly increased Fairly likely Greatly decreased
Peter Ellis Very unlikely Mildly increased Extremely unlikely Mildly increased Extremely unlikely Unchanged
Lindy Chamberlain Very unlikely Mildly increased Extremely unlikely Mildly increased Extremely unlikely Unchanged
Lucy Letby Very unlikely Mildly increased Extremely unlikely Mildly increased Extremely unlikely Unchanged

The question, then, is how many of the “little arrows” are inconsistent with another explanation. Here there are two categories of alternative explanation: that someone else was responsible, or that no-one was criminally responsible: the event would have happened anyway.

The prior probability of there being a different murderer on the ward is the same for any other nurse as for Lucy Letby: extremely unlikely. No suggestion was made that any other person was involved, so we can assume two alternatives: either an innocent explanation or Letby was the culprit.

It is worth also looking at the categories of circumstantial evidence in each case and associating it with one or other of those probabilities. Does it make it more likely that There was criminality involved in the deaths, or that, Assuming there was criminality, Letby was the culprit.

Relevance of evidence to probabilities
Evidence Criminality Letby was the culprit
Relevance Posterior value Relevance Posterior value
Ward roster No N/A Yes Weak
Post-it Note No N/A Yes Weak
Editing nursing notes to “cover tracks” Yes Weak Yes Weak
Post-event internet activity No N/A Yes Weak
“Trophy” handover notes No N/A Yes Weak
Bubbly personality No N/A No N/A
Obsession with a married doctor No N/A No N/A
Unexpected collapse Yes Weak No N/A
Insulin levels Yes Weak No N/A
Skin discolouration Yes Weak No N/A

Interestingly none of the “small arrows” point to both the presence of criminality and Letby’s particular involvement. It is worth reviewing the published pieces of the chief “public prosecutors” who make the case for Letby’s guilt. Among these are the expert witness Dr Dewi Morris, Daily Mail Journalist Liz Hull, BBC Journalist Judith Moritz and the frequently interviewed Criminologist David Holmes. They are emphatic in their dismissal of the “yellow butterfly gang” — in Hull’s words, “diverse band of fanatics and pseudo-scientists” coming from all “walks of society: well-to-do pensioners, middle-aged women, and the unemployed” and who, er, “counted scientists, neo-natal nurses, doctors and statisticians among their members” — so I was curious to see what they brought out as their clinchers.

Hull, on the New Yorker piece:

I’ve read the article and now the retrial is over I can write about it. And while there’s no doubting the author, who says she obtained full transcripts of the ten-month trial at huge cost, has researched the case thoroughly, it contains errors and cherry-picks evidence, omitting large parts of the prosecution case which was pivotal in reaching a conviction.

For example, it makes no mention of the 250 confidential “trophy” handover notes, blood test results and resuscitation notes relating to the babies police found at Letby’s home; it does not try to explain the Facebook searches that she made for the parents of her victims, years after she harmed their children.

Letby’s abnormal, animated behaviour in front of grieving parents after a baby died and pictures of cards she sent or received from parents of babies she murdered that were stored on her mobile phone, are also ignored, as is her obsession with a married doctor and her deliberate editing of nursing notes to make it seem like a baby was on the verge of collapse to cover her tracks.[1]

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