The present invention relates to a mind-altering substance testing unit. The unit includes a display module for displaying an indication of a drug or alcohol. A sensor module is releasably fastened to the display module and includes sensors for sensing the drug and alcohol. The unit also includes a sample cartridge for receiving a sample and for releasably fastening to the sensor module so that the sensor module can sense the drug. Advantageously, the same testing unit can be used to sense alcohol and the drug avoiding the need for separate testing units.
