Lugol’s iodine test detects the presence of vaginal epithelial cells. It is done on washings of the glans penis (or from moist blotting paper) of accused which is exposed to Lugol's iodine solution or iodine vapours. A positive test showing brown colour is due to the presence of glycogen in vaginal epithelial cells of the victim. Results can be elicited upto 4 days.