When a violent incident led young misfit garda John Sweetman into the Garda Technical Bureau with incriminating evidence, he found his true calling. He 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 tenacity and natural eye for detail 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 other crime scenes. He later employed his handwriting expertise in examining fraudulence, threatening letters and counterfeit documents, as well as the investigations into the 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, which peeks behind the curtain of how crimes are solved, and a bravely told story of a nonconformist detective in a remarkable career.

'I am determined this case is not going to be forgotten. This man is dangerous and has to be found.' From the prologue.

'A fascinating read.' Dr Marie Cassidy