A guide that aims to aid barristers’ understanding of statistics and probability and recognise ‘traps and pitfalls’ could help avoid miscarriages of justice, it has been claimed.

The guide, published today by the Inns of Court College of Advocacy (ICCA) in collaboration with the Royal Statistical Society, is designed to aid advocates’ understanding and interpretation of statistical evidence in trials. An ‘increasing amount’ of statistical evidence appears in expert witness testimony, the ICCA said. 

The guide helps identify the main traps and pitfalls that advocates are likely to meet when handling expert evidence.

According to the ICCA, having this knowledge is crucial in avoiding miscarriages of justice which ‘may have occurred in the past’ due to inappropriate use and understanding of statistics, by judges, witnesses and barristers.

In a statement the ICCA said: ‘Although the booklet does not claim to hold all the answers, it is hoped that it will encourage advocates to investigate further opportunities for professional development in the understanding, interpretation and presentation of statistical and probabilistic evidence. It should also help practitioners to consult more effectively with appropriate expert witnesses in the preparation of their cases, and know how to effectively deploy and challenge expert evidence and opinion.’

Lord Hughes, Supreme Court judge, said statistical propositions are ’sometimes beguiling, and at other times counter-intuitive’.

’All court users will benefit from a very basic guide to the kinds of question where statistical analysis can be useful, and, as importantly, to the kinds of question where it cannot,’ he said.

David Spiegelhalter, RSS president, added: ‘We hope this guide will ensure that evidence which includes statistics and data is used more effectively, for everyone’s benefit.’

The guide is available to download. Printed copies will be available next month.