Described is a method as well as an apparatus to prevent the starting or operating of a vehicle by a drug-intoxicated driver. The device is provided with a hand-held unit (1), which comprises a mouthpiece (2) for providing a breath sample and/or a saliva sample, an analysis unit (3) for determining the drug content of the supplied sample, at least one control unit (4) in which, depending on the determined drug content, a signal can be generated that can be transmitted to a control unit and/or switch unit, which is either internal or external to the hand-held unit, to influence at least one electric circuit of a vehicle, as well as a display (6) through which the driver is able to receive at least one message in relation to a test implementation and/or a test result. The described engineering solution is characterised in that the mouthpiece (2) is disposed at the front of hand-held unit (1), which faces the driver during the provision of the breath sample, and that the display (6) is disposed at the rear of hand-held unit (1), on the side opposite the mouthpiece (2), and that the message can at least some time be shown on the display (6) in such a way that said message is legible to the driver in plain text when looking into the rear vision mirror (7) of the vehicle. (Fig. 1) 1/1 2013_1113DE rr~1 1 6,6 a) b) Fig. 1 Fig. 2
