A non-invasive method and an apparatus for detecting drug ingestion based upon the effects of drugs on corneo-retinal potential and/or brainwaves. The method comprises the steps of (a) determining a plurality of reference waveforms, each including corneo-retinal potential (CRP) and/or brainwave waveforms corresponding respectively to a plurality of drugs, (b) recording a subject's waveform while the subject is subjected to a static positional test, and (c) comparing the subject's measured waveforms with the reference waveforms to determine which drug or combination of drugs was ingested by the subject. The apparatus includes an improved electronystagmograph (ENG) machine modified to include longer leads and increased gain (amplification) than typically used for conventional applications.