RSS publishes report on dealing with uncertainty in medical “murder” cases

The RSS has published a report tackling statistical bias in criminal trials where healthcare professionals are accused of murdering patients. Following several high-profile cases where statistical evidence has been misused, the Society calls for all parties in such cases to consult with professional statisticians and use only expert witnesses who are appropriately qualified.  
 
The report, ‘Healthcare serial killer or coincidence?’, is produced by the RSS’s Statistics and the Law Section. The group evolved from a working group of the same name set up in early 2000s after the Society wrote to the Lord Chancellor and made a statement setting out concerns around the use of statistical evidence in the case of Sally Clark.  
 
According to the report, suspicions about medical murder often arise due to a surprising or unexpected series of events, such as an unusual number of deaths among patients under the care of a particular professional.  
 
The RSS has major concerns about use of this kind of evidence in a criminal investigation: first, over the analysis and interpretation of such data, and secondly over whether it can be guaranteed that the data have been compiled in an objective and unbiased manner.  
 
When interpreting such data, investigators need to consider: 
  • Could the deaths have occurred for reasons other than murder?  
  • If murder was the cause, is the person under suspicion responsible?  
The report also calls for more care to be taken by experts to avoid drawing erroneous inferences from such data, by properly controlling for plausible causal factors. 
 
The RSS’s concerns about the compilation of the data used in such investigations are that attention is rarely given to ensuring that unconscious bias has not influenced the selection of cases. Such innocent cognitive biases are prevalent throughout society and control of these needs active steps such as blinding. For medical misconduct cases, the report recommends that investigations should be supervised by expert panels independent of both the suspect and their employer. 
 
RSS CEO, Stian Westlake, commenting on the report, said: ‘We have seen cases across the world of people wrongfully charged based on incorrect statistical analysis. We’re calling for better collaboration between the legal and statistical communities to prevent such miscarriages of justice happening in the future.’  

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