When a violent incident in his stationed town led John Sweetman into the Garda Technical Bureau with incriminating evidence, the course of his life changed dramatically. As a young garda struggling with personal demons, he went from being on verge of leaving the force to finding his true calling.

John spent the next 25 years as a detective garda working on the frontline of crime scene investigations - as both a fingerprint expert and, in later years, a forensic handwriting and document expert. His natural eye for detail and tenacity led him to becoming involved in many criminal investigations and high-profile cases.

From the brutal murder of Marie Dillon in Finglas in 1998 to the gangland killing of Raymond Salinger in 2003, John was involved in the search for forensic evidence at these, and numerous other, crime scenes. He later employed his handwriting expertise in the investigation of fraudulence, threatening letters and counterfeit documents, as well as the investigations into the callous murders of Jasmine McGonagle and student Jastine Valdez and the horrific Hawe familicide in Cavan in 2016.

Identity is both a fascinating insight into specialist forensic fields - that peeks behind the curtain of how crimes are solved - and a bravely told story of a misfit detective in a remarkable career.