Motorists charged with DUI (driving under the influence) or a DWI (driving while intoxicated) should understand that a Breathalyzer — a breath-alcohol chemical test — is one of several pieces of evidence that can be used in a court of law. Passing a Breathalyzer does not guarantee acquittal, nor does failing such a test guarantee conviction.
Research by the National Highway Traffic Administration has identified twenty symptoms that may indicate a person is driving while intoxicated. These driving patterns give a police officer probable cause to stop a vehicle and further investigate for DUI. Sworn testimony from an arresting officer, in addition to video footage of the vehicle prior to the stop, may not be compelling evidence by itself, but may serve as the basis for a case.
Statements from the driver are also admissible evidence. When asked how many drinks you've consumed, unless you can honestly say you've had nothing, it is typically wise to politely decline to answer questions until you've spoken to an attorney. Admitting to having any number of drinks will be included in the police report, and will be used against you in court. Furthermore, your attitude will be noted along with other physical symptoms of intoxication; if you are excessively hostile or jovial, your demeanor will weigh against you in court, so it is important to be as professional with the police as possible.
When asked to participate in a Breathalyzer test, you are generally required to comply. Refusing to submit to any chemical test — Breathalyzer, blood test or urinalysis — may be permitted by law, but will typically be admitted in court as "consciousness of guilt." Failing a Breathalyzer with a blood alcohol content (BAC) of .08 or higher will result in immediate arrest; in some states, your license may be summarily suspended at the time of arrest. Furthermore, state laws typically allow a driver to be charged with DUI for a BAC between .05 and .07.
The Breathalyzer measures alcohol vapor in the driver's breath, and is the most commonly administered chemical test for DWI or DUI suspects. The Breathalyzer multiplies the chemical trace by roughly 2,100 to determine BAC. The equipment has several drawbacks, however, so the results are not generally enough to convict without other evidence supporting intoxication.
A Breathalyzer presumes the entire volume of air being measured is from the driver's lungs. It is therefore susceptible to falsely elevated measurements from any alcohol trapped in the mouth or esophagus. Alcohol may be retained in dental work, such as bridges or caps, and may remain in the esophagus after vomiting or due to any sort of gastric reflux disorder. Mouthwash, breath mints and other products may also contain alcohol and cause an erroneous Breathalyzer result.
It is important to note that alcohol is not instantaneously absorbed into the blood, so Breathalyzer results can sometimes be refuted with a "rising BAC" defense. A test that is delayed up to an hour after the initial stop may indicate intoxication, even though the alcohol had not been sufficiently absorbed at the time of driving to cause impairment. This argument works both ways, depending on the delay between the driver's last drink and the administration of the test; the driver must be proven intoxicated while actually driving.
Police may administer a variety of field sobriety tests (FST), often recorded on video, to further support DUI charges. These tests are typically administered after an officer has decided to make the arrest for the sole purpose of building a more solid case when the driver fails. This supporting evidence may be used to counter claims that a Breathalyzer was inaccurate due to improperly calibrated equipment or other anomalies. Field sobriety tests are intended to highlight clear physiological or mental impairment, but they can be misleading if the driver has other disabilities that may interfere with passing the tests.
Furthermore, a police officer is not a medical professional, and is therefore not qualified to expertly judge certain physical responses. For example, the horizontal gaze nystagmus test — requiring a driver to visually follow a pencil, finger or penlight — is often inadmissible in court because an officer cannot reasonably determine nystagmus, an abnormal eye jerking or oscillation, or its angle of onset. This is the sort of evidence — combined with driving footage and self-incriminating testimony — that may lead to conviction despite a passing Breathalyzer result.
You may have the right to request an independent blood test to determine BAC. A blood test is the most reliable measurement of blood alcohol content, and the results may be used to defend against Breathalyzer results that might otherwise lead to conviction. While you may be required to cover the cost of an independent test, it is often worth the expense to provide a strong DUI defense.
Understanding your rights is crucial to defending against any DUI or DWI charge. Remember that you are innocent until proven guilty beyond a reasonable doubt. A Breathalyzer is only one piece of the puzzle, and you are largely in control of which other pieces can be admitted in court. Choose them wisely!
