Once you have been detained (stopped) and an officer believes you are under the influence they will ask you incriminating questions such as "How much have you had to drink?", "What did you have to drink?", and "What have you eaten in the last 24 hours?". It is important to know, you do NOT have to answer any questions and if you do answer these questions, the answers will be used against you in court, even though the Officer was not required to read you your rights because you have not been officially "arrested". This "right" to remain silent should be done in a courteous and deferential manner and should not be confused with submitting to the "official" chemical test at a later time. Note, you MUST submit to a chemical test of your breath or blood (urine is not available anymore except if the officer elects it as a last resort such as no other working equipment) in order to avoid losing your license for one year and complicating an already difficult situation.

If the officer believes you are under the influence, he will ask you to perform some field sobriety tests. It is important to know, you are NOT obligated to submit to any field sobriety tests (i.e., horizontal gaze nystagmus, one leg stand, touching finger to nose, walking straight line, etc.). Also, you should know, many law enforcement agencies (like the California Highway Patrol) use in-field breath devices (preliminary alcohol screening devises, PAS for short) as a "field sobriety test" and as a way to gain evidence against you after your arrest. It is important to understand that in almost every case, you are not required to submit to this in-field breath device (unless you are under 21, in which case you must submit to this test). The officer is supposed to tell you of the test's voluntary nature, however this admonition is many times overlooked, intentionally or not.

Once the "stop" has escalated past a "detention" and into a custodial arrest you must be read your Miranda rights (you have the right to remain silent, etc) and you may request a lawyer before speaking to police. However, you are not entitled to speak to a lawyer or have a lawyer present before or during your submission to a chemical test as required by California 's implied consent law. If you were not read your Miranda rights, after being placed in custody, any statements you made to the officers may be challenged in court. This may weaken the case against you, but rarely results in a dismissal in and of itself.

When deciding what test to take you should know that blood tests are generally more accurate than breath tests, both are more accurate than urine tests. Also, blood tests must be saved and made available to your attorney for independent testing while the ability to retest a breath sample is lost forever as the breath machine does not save a sample of the breath. However, breath tests can be challenged in court by an attorney who knows and understands the machines and how they operate and where problems exist. Also, there are inherent (allowable by law) acceptable error factors with both machines and both must keep records showing they were regularly calibrated and maintained.