How can they prove you violated penal code 11550a hs?

11550(a) of the California Health & Safety Code makes it unlawful to be under the influence of certain drugs. The prohibition applies anywhere - on the street and in your home. Most drugs cause the human body to react in specific ways, such as dilating/constricting the pupils, increasing the pulse, causing the eyelids to droop, making the user very excitable or very sleepy, et cetera. Many officers are trained to recognize these signs and symptoms of drug influence. They prove their case by documenting their observations of the alleged drug user, the suspects admissions, and the results of the suspects urine test that is mandatory under California law when arrested for violation of this law.