The boundaries of simulation and dissociative amnesia are thin and not rarely unclear. Diagnostic criteria and a thorough clinical history are sometimes not enough to shed light on the nature and essence of one's will and conduct. Throughout history, psychiatry has been challenged to testify before society over patients’ truth and deceit. Do they share common grounds or must we accept that uncertainty is the inevitable price of truth?

The authors present a clinical case of a young man coming to the emergency services with multiple lacerations in the upper abdomen and limbs, referring “amnesia” for the last five years of his life. The patient had no previous psychiatric record or any known family or social dysfunction. Approach, management and diagnosis are discussed.