School of Mathematics

Forensic statistics in the Guardian

Colin Aitken, professor of forensic statistics, speaks in the Guardian about why he hopes the Appeal Court will reconsider a recent ruling on the method for the evaluation of shoemark evidence.

http://www.guardian.co.uk/law/2011/oct/02/formula-justice-bayes-theorem-miscarriage/

Bayesian statistics is used to update our estimates of the likelihood of an event when given new evidence related to it. In court cases, a jury may have a belief about whether the defendant is innocent or guilty, and Bayes Theorem tells them how much to adjust this belief based on new evidence (for example, a matching DNA sample or matching shoe-prints). However, a judge has now ruled that Bayes Theorem cannot be used in court unless the statistics are "firm".