We have previously described photochemical fingerprinting as an effective tool for structural discrimination of individual SCs. That is, inducing a photochemical change in the analyte and using the altered emission profile as a characteristic presumptive identifier of the analyte. Speculatively, we were interested to explore if a similar phenomenon could support differential detection of CBD and THC. Figure shows a time-course plot of spectra collected for THC in EtOH at 0.1 mg/mL. We find that continuous irradiation at 265 nm causes the emission band of THC to rapidly undergo a notable structural change, where three new spectral features emerge centered at ~365 nm, ~380 nm and ~405 nm. It is logical to suggest that the observed shift in emission arises from a photochemical reaction that results in production of new fluorescent species. Moreover, from Figure , CBD does not produce similar, or indeed any new spectral features, at least under the conditions used here. That is, under the same conditions, the emission band of CBD remains unchanged, thus providing a means to discriminate the two cannabinoids. This is serendipitous because, at least in the UK, CBD is legal and THC is illegal.