21 in the course of a prosecution, problems in terms of statistical interpretation of unusually high incidences of death, and the use of contentious and novel constructs.
ausdoc. com. au 18 JULY 2025
21 in the course of a prosecution, problems in terms of statistical interpretation of unusually high incidences of death, and the use of contentious and novel constructs.
One of the most contentious issues in the prosecution’ s case was the evidence from Dr Sandie Bohin, who created what has been described as the Bohin criteria.
This was described as a collection of warning indicators that when viewed together implied purposeful injury, rather than natural causes.
The combination included abrupt deterioration in the health status of previously well newborns, odd colouring— namely a deep purple / red mottling, resistance to resuscitation attempts, inexplicable air in the stomach or circulation, and bloody discharges from the mouth or nose.
What Dr Bohin maintained was that, if those warning indicators coincided, that was highly suggestive of purposeful injury rather than death by natural causes.
There was also the forensic psychology evidence about healthcare serial killing.
That construct is contentious within forensic psychology. Like many areas of profiling, it is an area of significant disputation among experts of good repute and competency.
AD: Is it fair to say there were deficiencies in the prosecution’ s expert evidence then?
Professor Freckelton: I think it would be premature to classify the evidence as deficient at this stage. This is a very heavily contested set of issues in which there are plausible views on either side.
What can be said though is that the analy sis of the statistical unlikelihood of so many deaths is problematic, because there may be confounding variables which may have explained the high number of deaths during that period.
Notably, there had been another spike in deaths previously. Similarly, there are spikes in deaths in other hospitals.
So, there are risks in drawing too ready inferences from this.
The Professor Lee analysis has also suggested alternative theories consistent with innocence for the abnormalities of insulin, which can arise from other causes, and also the presence of air in tubes, which can result from faulty technique.
In short, the issue is whether there are other explanations for what are inculpating analyses by the expert witnesses, and whether now, with the benefit of deep scrutiny by international experts, it has to be said that there is a reasonable doubt in relation to the prosecution’ s case.
AD: I know it is a familiar question, but can you explain how expert evidence is used in these complex medical cases?
Professor Freckelton: The first question is whether it’ s relevant, and the next question is whether it carries the status of expert evidence.
The yardstick that we use in Australia is whether it is the product of specialised knowledge based on skill, training or experience.
Then it goes to the jury as part of the amalgam of evidence. in this case satisfied that yardstick. The difficulty lies more with whether the experts came with a confirmation bias, made inappropriate assumptions, or they used, as part of their analyses, novel modes of reasoning, such as Dr Bohin.
When these issues arise, it’ s not because of a cynical hunting of experts of a particular view.
The real focus in reviewing such evidence is whether, on the basis of what was expressed, that there were flaws in reasoning processes and risks that the jury may have drawn wrong inferences from the evidence given and the directions provided by the trial judge.
AD: What about the defence’ s case— we’ ve seen media reports that they did not call any expert witnesses to challenge the clinical evidence. Is this true?
Professor Freckelton: As far as I understand it, that is straight-out wrong.
The prosecution’ s evidence was heavily contested. The defence called a 30-year experienced neonatologist, an endocrinologist, a paediatric radiologist, and so on.
This is a trial that took some 10 months, and the defence not only called the accused,
who gave evidence for an extraordinary period of time, but also called expert witnesses in the usual way.
AD: The defence’ s argument is that much of the evidence, as you pointed out, was circumstantial.
Professor Freckelton: Yes— one of the limbs of the prosecution’ s case was how unlikely it was that there would be this number of deaths that were not readily explicable, suggesting that the inference to be drawn was that this was purposeful homicide by the one person who was present on each occasion.
That’ s always a dangerous argument, because there are risks of wrong inferences being drawn, but a key point to make in this regard is that it is just one piece of evidence.
It doesn’ t mean she was guilty purely because of that— that was one of the strands in the prosecution’ s case, and there were multiple different strands relating to a range of other factors.
The answer by the defence in respect of each one is that there is another hypothesis consistent with innocence.
For example, she was depressed, so that is why she wrote strange things in the notes.
Or, she was conscious of the numbers of children dying and so she started doing digital searches on the issue, as others may or may not have been doing at the time given
‘ The analysis of the statistical unlikelihood of so many deaths is problematic.’
the worry that may have been prevalent within the hospital about the incidence of neonatal deaths.
So the question ultimately is, on the basis of all of the evidence, does the jury or do the jurors individually have a reasonable doubt in relation to the innocence?
Clearly, two of them did, but 10 did not.
AD: Do you think this type of case should be heard by a jury, given that jurors may not have the specialised medical knowledge to fully understand the expert evidence?
Professor Freckelton: The difficulty is the alternative. The only other option is that it be a judge-alone trial on the basis that the material is too complex or the task is too burdensome for jurors.
Like many, I’ m loath to abandon trial by jury and leave it in the hands of a single person.
The advantages of a jury are that they use their common sense and that there are multiple perspectives being brought to bear. If it’ s a single judge, it’ s one person.
It may well be that the one judge who picture credit is legally experienced and trained does not have a great deal of knowledge in relation to forensic endocrinology or psychology— some of the fairly abstruse and recondite [ subjects ] which were traversed at length in the Letby trial.
The advantages of a judge are that they are accustomed to weighing conflicting expert opinions, and they may be less influenced by the articulateness or superficial impressiveness of an expert.
This case is certainly shining a very bright light on how demanding a task it is for a jury over a multi-month trial, with such complex, conflicting expert evidence, to discharge their function.
AD: Any final thoughts?
Professor Freckelton: There have been occasions where issues of novel evidence, where unusual areas or particularly contentious areas are the subject of the expert opinions, have resulted in miscarriages of justice being found by the courts.
There are certainly areas of real substance here which may fall into the category of being so problematic as to suggest there has been a miscarriage of justice.
But it emphasises how extraordinarily demanding the task is for the prosecution and defence, but most particularly for the jury, where there is this extent of complex evidence, which for anyone is very hard to evaluate.
It remains to be seen what the commission thinks of the information before it. When that becomes public, we will be in a better position to have an informed discussion.
The matter may go to the Court of Appeal, or it may not.
Professor Ian Freckelton.
GETTY IMAGES
AD: Are expert witnesses chosen on the basis that they align with a particular narrative?
Professor Freckelton: The ethical responsibility of the prosecution is to find suitably qualified and experienced experts. Most assuredly, the experts called by the Crown
Professor Shoo Lee reads out his expert evidence report on the Lucy Letby case at a press conference in London.