- Driving Symptoms: Reckless driving, weaving in a lane, or switching lanes rapidly are some signals. You can see a list of indicators from the National Highway Traffic Safety Administration.
- Behavior and Appearance: Signals of intoxication include the smell of alcohol in the breath, slurred speech, and even an unkempt personal appearance.
- Field Sobriety Tests: There are a wide variety of these tests [reciting alphabet, fingers-to-thumb, hand pat, horizontal gaze nystagmus (following an object such as a pen or finger from side-to-side with your eyes)] even though federal studies show that just three tests are effective: the walk-and-turn, one-leg-stand, and nystagmus. Nationally, police are adopting these three standardized tests, but in California, officers still administer the tests that have been proven unreliable. Despite what you may have heard, you can refuse to take these tests without legal consequences.
- Incriminating Statements and Miranda: The officer can ask incriminating questions before an arrest, during their initial investigation. Miranda warnings need not be given until after an arrest.
- Blood Alcohol Test: These tests can be conducted by a breath or blood test. Often, the Preliminary Alcohol Screening (PAS) units, also known as the Evidential Portable Alcohol Systems (EPAS), are administered as part of field sobriety tests. However, taking these are not legally required (unless you are under 21) until after an arrest is made.
There are five categories of symptoms for driving under the influence of alcohol, drugs, and marijuana.