The first thing an officer looks for during a traffic stop, are objective signs of intoxication (OSIs), including bloodshot, watery, red eyes; the odor of alcohol; thick or slurred speech; flushed face; fumbling with a wallet to get the driver's license; leaning on the car for support; unsteady gait; difficulty following directions; etc. Remember, every traffic stop is a potential DUI investigation in the mind of law-enforcement officers, so they will look for anything to suggest a driver may be under the influence, thereby justifying further investigation.
If an officer does observe OSIs, he or she will then ask a series of questions, designed to create a drinking pattern, which will almost certainly be used against the driver. Further, the questions are designed to produce evidence that incriminates. Most people, under the stress of the detention, tend to provide inaccurate information. It is completely understandable behavior, but to a prosecutor, it represents consciousness of guilt. Given the above, it is generally wise to invoke your Fifth Amendment right to remain silent with respect to any questions posed by officers during a DUI investigation; all the information a driver MUST give is contained on your driver's license.
The next step in a DUI investigation is the administration of field sobriety tests (FSTs). These may include walk-and-turn, touch-the-nose, one-leg-stand, modified position of attention (the Romberg Test), horizontal gaze nystagmus (following an object such as a pen from side-to-side with your eyes while keeping your head still), fingers-to-thumb and hand pat. The only purpose of these tests is to allow law enforcement to collect more evidence to convict you. There is no legal requirement to perform such tests, and without such evidence, the job of the prosecutor becomes more difficult.
Many police agencies are using a roadside breath-testing device (Breathalyzer) as an additional field sobriety test. The Preliminary Alcohol Screening (PAS) units are handheld devices that are supposed to provide a crude indication of the suspect's blood alcohol content (BAC). These units are designed to aid the officer in making a probable-cause determination as to whether the subject is intoxicated. However, if a subject burps, belches, vomits or regurgitates within 15 minutes prior to the administration of the test, the result will be grossly inaccurate and inflated. Unlike the evidential chemical test, which will be discussed below, there is no legal obligation, on the part of the driver, to take a PAS test unless it is administered after arrest.
The final step in a DUI investigation is the evidential chemical test. Drivers are required to take this test under California's Implied Consent law. That means, if you are driving on California roads, you are implicitly consenting to chemical testing, if a law-enforcement officer has probable cause to believe you are DUI. If you refuse to take this test, you will be arrested for DUI, and if you are convicted, you will face much harsher penalties.
The evidential chemical test involves a choice of breath or blood. There are a number of different brands of breath machines used in California, but all are vulnerable to numerous problems and none of them can be relied upon as accurate. For one thing, the computer in the Breathalyzer makes many assumptions.
For example, it assumes the person being tested has "average" physiology and metabolism, when, in fact, physiology and metabolism vary greatly from individual to individual. Blood analysis is far more accurate, although other potential problems exist, such as fermentation or coagulation of the sample and lack of sterilization during the blood draw. However, the advantage of a blood sample is that a defendant is able to obtain a split of the sample for independent testing.
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While the above is a thumbnail sketch of a very complex and nuanced area of law, should you ever find yourself the subject of a DUI investigation, it may nonetheless be helpful to you. What will prove even more helpful is hiring an attorney to zealously defend your case.
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This article appeared in print as "A Driver's Guide to DUI Stops."