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.

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".