Driving under the influence of alcohol or drugs is not illegal, unless your ability to drive is impaired. Because everyone’s ability to drive without impairment after consumption of alcohol varies, each DUI case is unique. The basic approach of the law to proving this crime is to measure the amount of alcohol in one’s breath and then make two inferences from that measurement. First, the amount of alcohol in one’s bloodstream is inferred from the amount of alcohol that is detected in your breath. Second, the degree of impairment of your driving ability is inferred from the level of alcohol in your blood. In other words, the law assumes that the amount of alcohol in your bloodstream directly corresponds to the impact that alcohol is having on your brain and it’s judgment; thus upon your nervous system’s ability to issue the signals that tell your limbs to perform functions like pushing the brake pedal or turning the steering wheel.
Yet, there are further inferences that have to be made to find that you are guilty of the crime. The officer who is attempting to enforce the law next makes the inference that the degree of impairment he has inferred from the test is the same degree of impairment that existed at the time you were operating the motor vehicle.
The officer is assuming that there is a direct correlation between the amount of alcohol in your bloodstream and you ability to operate a vehicle. Because the officer has no information on your individual ability to operate a vehicle, he is also making the assumption that your skill is within the range of skill held by the average driver.
Basically, the law is attempting to make a highly individualized and complex determination (whether your driving ability is impaired) appear to be as simple as determining whether .80 is a higher number than .10.
The a KEY point you need to understand that all of the above-explained inferences are based upon information that YOU voluntarily give the officer. When you agree to submit a sample of your breath or blood, you essentially lay the first brick upon which the officer builds the wall of his case- brick by brick, or actually by, inference upon inference. You have the Constitutional Right to refuse to talk to the officer or to give him a sample of your breath.
Unless you believe the officer is going to give you the benefit of any doubt in making all those inferences, you should decline to provide a breath sample.