Abstract: A method for identifying a test subject being tested for consumption of a selected substance includes storing in a database of a facial recognition processing system a gallery of facial images of a set of individuals. The facial recognition processing system receives a facial image of a test subject being tested for consumption of the selected substance and compares the received facial image with at least some of the facial images in the stored gallery by executing a facial recognition algorithm. In response to a match between a facial image in the stored gallery and the received facial image having a predetermined level of match certainty; the facial recognition processing system identifies the test subject. In response to a failure to obtain a match between a facial image in the stored gallery and the received facial image having a predetermined level of match certainty, the facial recognition processing system flags the received facial image for subsequent manual analysis.