Hi, Gilbert Syndrome does not affect the processing of most of the substances as well as foods, as no particular abnormality is present except for the absence of an enzyme required for conversion and finally excretion of bilirubin from the body resulting an increase in levels of non-conjugated bilirubin. Therefore you cannot take a plea in your favor by showing that your son has gilbert syndrome. He will be proved guilty equally, if found to have illegal substances in his body system. Take care. Hope I have answered your question. Let me know if I can assist you further. Regards, Dr. Satnarain Bansal, General & Family Physician