# RSS and ICCA publish guide to statistics for legal professionals

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The Royal Statistical Society and the Inns of Court College of Advocacy (ICCA) have just published a guide to statistics specifically for barristers and others working in the legal profession, to coincide with European Statistics Day which takes place today.

The 75-page guide, Statistics and probability for advocates: Understanding the use of statistical evidence in courts and tribunals (published on the RSS website), provides a brief overview of statistics when applied in courts of law, and it is hoped that it will help lawyers assess their evidence critically, therefore enabling them to challenge any interpretation of statistics or probability statements where there may be cause for concern.

The book identifies pitfalls that advocates are likely to meet when handling statistical evidence, such as misunderstandings of probability (famously seen in the tragic case of Sally Clark a number of years ago), conflating correlation/causation and the difference between absolute and relative risk.

The book also includes a chapter introducing the basics of statistics, probability and the scientific method.

A third chapter provides advice on putting it all into practice, including case studies in different areas of law to show how advocates might go about questioning expert witnesses.

The final chapters focus on potential developments in this area and detail resources to further advocates’ knowledge and understanding and confidence in using statistics and probability in court.

As only a minority of advocates will have studied mathematics or science to a higher level, it is hoped that the guide will encourage more consultation with appropriate expert witnesses when preparing cases.

Lord Hughes, an judge of the Supreme Court, welcomed the guide. 'Advocates (and judges) very often encounter experts who use statistics in their reports. An understanding of the terminology which they use is an essential baseline from which to start in following and evaluating what they say. More importantly, 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. This guide has been prepared with these aims in mind, and by experts who have set out to explain themselves to lawyers. It will, I hope, be a valuable companion to those who are asked to digest, to apply, and to test, expert opinion relying on statistics.'

Also commenting on the guide, RSS president, Sir David Spiegelhalter said: 'The RSS welcomes the Inns of Court College of Advocacy’s programme to improve the reliability of expert evidence, and we hope this guide will ensure that evidence which includes statistics and data is used more effectively, for everyone’s benefit.'

Derek Wood QC who chairs ICCA’s Board of Governors, said: 'The Inns of Court College of Advocacy is proud to have collaborated with the Royal Statistical Society over the production of this booklet. Experts in every type of discipline, appearing in every type of court and tribunal, habitually base their evidence on statistical data. A proper understanding of the way in which statistics can be used – and abused – is an essential tool for every advocate.'

The guide, Statistics and probability for advocates: Understanding the use of statistical evidence in courts and tribunals is published on the RSS website.

David Spiegelhalter Statistics and the Law section