Abstract: The invention relates to a device for preventing identity thefts, in order to avoid the starting of mechanical apparatus, such as a vehicle (automobile or similar), or the switching-on of electrical, electronic or electro-medical equipment, if the user is not the authorised user or if the physical conditions necessary to guarantee the safety of the user or other people are not met. The device comprises: a first module comprising a mouthpiece for the acquisition of data such as blood alcohol concentrations or exhalation pressure, a second module provided with a central processing unit, and a third module for capturing images of the eye of the user, provided with a microcamera and means for illuminating the eye. The preferred distance between the eye of the user and the microcamera is between 2 cm and 5 cm.