Fathom by Mikel Parry

Demo Ward is different in his unique ability to solve cases by assimilating the criminal mindset using little to no evidence. A top-secret invention is revealed to Demo that will change his life forever...Fathom. Now he not only assumes the mindset of the criminal but enters it directly. His ability and dumb luck have carried him through years plagued with guilt after the devastating loss of his partner and best friend. However, now he replaces himself tangled up in the case of the century as he faces his own demons. Decades of murder, lies, and deceit now come crashing into his world, and Demo is forced to solve an unbreakable case while using the warped mind of an elusive psychotic killer.