“Presumptive impairment” occurs in situations where 1) a police officer observes some behavior on your part that would give the officer a valid reason to temporarily detain you in order to determine if you are driving under the influence and 2) there exists some legally-defined “lower limit” where, if you are found to exceed this lower limit, the law presumes you to be guilty of driving under the influence.
Although there is some state-to-state variability in what Blood Alcohol Concentration (BAC) level is required to make a DUI case based on presumptive impairment there are, in fact, two BAC levels that can apply to your case, depending what type of driver’s license you possess:
1) If you have a Commercial Driver’s License (CDL), a BAC of 0.04% or greater is sufficient to establish presumptive impairment and thus to convict you on a DUI charge. This is a federal regulation and must be adhered to by each state regardless of what a particular state’s law defines as presumptive impairment.
2) Practically all states, including New York, define presumptive impairment to be a BAC of 0.08% or greater for any other type of license or driving privilege although each state has the authority to set its own definition of the BAC that it will use.
Does a BAC below the level of that required for presumptive impairment mean that I can’t be prosecuted for DUI?
No, because the law makes a “presumption of impairment” and not a “presumption of sobriety!” Impairment is defined by many factors such as drowsiness, ability to concentrate on tasks, and awareness of one’s surroundings. These other factors are usually noticed during a field sobriety test. While a BAC above a certain level is all that is needed to convict on a charge of DUI, if you exhibited other signs of impairment, you can still be found guilty of DUI based on those other signs.
Are there defenses against a DUI charge based on presumptive impairment?
There are several defenses that can be used if you are charged with a DUI that is “proven” by presumptive impairment. These include 1) an invalid reason for a police officer to have made a traffic stop, 2) an incorrect interpretation of field sobriety tests, and 3) failure to administer an accurate test to determine the blood alcohol level.
Many DUI arrests are “thrown out” because the arresting officer did not have a legitimate reason for making a traffic stop which, in turn, led to a DUI arrest. As an example, you could be stopped for a traffic violation if you failed to use your turn signal at least 150 feet prior to making a turn. Failure to do so is not sufficient grounds to suspect that you might be impaired. Under the rules of evidence, everything discovered after such a traffic stop cannot be used in a criminal court.
Almost everyone is familiar with the “follow my finger,” the “count backward from 100 by sevens.” and the “blow into the balloon until I tell you to stop” activities that usually accompany a DUI arrest. What many people are unaware of is that none of these tests, taken together or by themselves, are sufficient to prove a DUI charge. They can be used to establish probable cause but are not proof that you were or even presumed to be impaired.
There is only one type of test that is considered accurate enough to be taken as absolute proof that someone was impaired by alcohol, and even this test must be performed in a medical laboratory that is certified to very exacting standards. By this we mean only a test that is made directly on the blood of the driver. Many states will accept the results of tests that are made using sophisticated machines such as a “Breathalyzer,” which can very closely approximate the amount of alcohol present in the bloodstream. However, this test must be administered by a trained operator using a properly maintained and precisely calibrated machine if the results obtained are to be considered as being accurate.
In any case, specific questions related to presumptive impairment should be addressed by a qualified criminal defense attorney.