In this episode of Lines of Enquiry: Case Notes, former Garda Detective Sergeant Alan Bailey takes us inside the hidden world of cold case investigation. With more than 200 unsolved homicides sitting on the desks of just eight detectives, he explains how and why an investigation goes cold, what it takes to justify reopening a case, and why there is always still hope.

Alan talks through some of the most significant cases he worked on, including the murder of Nora Sheehan. He reflects on the impact of modern forensics and the importance of preserving evidence, that allowed this case to be solve four decades after it happened.

Having been a lead detective on Ireland’s most prolific missing women cases, which became known as the Vanishing Triangle, Alan shares the immense challenges of working on cases with no suspect, and sometimes no body. After searches for some of these women began again recently, he shares what it takes to trigger new digs and how seemingly minor details can suddenly become pivotal.