You the jury - Is this case a prosecutor fallacy or not?

Date: Monday 20 October 2025, 5.00PM - 7.00PM
Location: Online
Online
Section Group Meeting
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In this event, Nigel Marriott (CStat MAE) will give an interactive talk on the Prosecutor's Fallacy. He will describe a case he has worked on as a statistical expert and the audience will have the chance to vote on the likelihood of guilt as each piece of evidence is described. He will also discuss the Sally Clark case and why he thinks statisticians have drawn the wrong lesson from this case.
 
The prosecutor’s fallacy confuses the probability of finding the evidence on an innocent person with the probability that a person on whom the evidence is found is innocent” - The Inns of Court College of Advocacy joint publication with the Royal Statistical Society on Statistical Evidence page 22, 2019  
 
When statistical evidence in a case indicates a very low p-value, it doesn’t automatically mean the case could be a prosecutor fallacy.  What matters is how the p-value is interpreted alongside the other evidence in the case.
 
In this talk, you will get the chance to be the jury!  Based on a case Nigel testified in as a statistical expert, you will first hear the statistical evidence he presented followed by 6 more pieces of evidence from the prosecution and defence.  After each piece of evidence, you will have the chance to vote on the likelihood of the defendant being guilty of the charge.  There will then be a chance to discuss why you voted the way you did before Nigel reveals the actual verdict and its implications.
 
Nigel will then discuss how his experience in this case led him to reconsider the infamous Sally Clark case.  He will explain why he thinks statisticians have drawn the wrong lesson from this case and others.
 
 
Nigel Marriott CStat MAE
 
 
Contact Amy Wilson
 
 
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