Basically, to prove that someone is under the influence of marijuana, the prosecution looks into one’s driving pattern, one’s personal appearance, one’s performance in the Field Sobriety Test of FSTs, and one’s results from a chemical test that would reveal of marijuana is indeed in one’s bloodstream. The first three sings can be introduced through a testimony given by the arresting officer
The arresting officer will testify in court and state their reasons on why they believe that you are driving under the influence of marijuana.
The testimony for pulling over a driver for suspected marijuana ingestion and then driving can be backed up by the following signs that are usual indicators of driving under the influence: driving into opposing or crossing traffic, straddling center of lane marker, turning with a wide radius, weaving, almost colliding with an object or vehicle, drifting, breaking erratically, slow response to traffic signals, turning with a wide radius, driving with headlights off, turning abruptly or illegally, appearing to be drunk, following too closely, swerving, stopping inappropriately, speed more than 10 mph below the limit, driving on other than designated highway, stopping without cause in traffic lane, tires on center or lane marker, and accelerating or decelerating rapidly.
The physical aspect or one’s personal appearance can be judged through the following indicators: dilated pupils, elevated pulse rate, elevated blood pressure, giving off the odor of marijuana, eyelid and body tremors, relaxed or uninhibited demeanor, dry mouth, and short-term memory impairment.
One’s performance in the different field sobriety tests are also indicators. These tests are not tests, per se, but are physical agility exercises that determine your control over critical skills that may be involved while maneuvering a vehicle. There are five tests: 1. Nystagmus: The officer will hold an object 12 inches from the driver’s face, then move it side to side. The driver must follow the action with his eyes, while the officer looks out for involuntary trembling or jerking of the eyeball; 2. Walk and Turn. This is used to test whether the driver can keep his balance, follow instructions, and remain dexterous. The driver is instructed to take nine heel-to-toe steps along a line, then to turn, and then to take nine hell-to-toe steps back.; 3. Standing in One Leg. This is used to test balance and attention. The driver is made to stand with the heels together, arms on the side, and then while counting out loud, he has to raise one leg at least 6 inches from the ground; 4. Finger to Nose. The driver is required to place both feet together and stand straight, and with their eyes closed, bring the index finger to their nose, when ordered by the officer; 5. The Rhomberg Balance Test. The driver is made to stand in attention, with eyes closed, and their heads tilted back for 30 seconds. The officer is gauging their ability to stand erect steadily without muscle tension.
If the accused is not able to perform the FSTs to satisfaction, he is then asked to do a breath test, via a breathalyzer. If he passes the breath test with a relatively low BAC, then the officer may ask for the DRE to come to the scene and aid in the investigation.