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NEW YORK DRIVING WHILE INTOXICATED – PROBLEMS WITH RETROGRADE EXTRAPOLATION – PART 1

Driving While Intoxicated in New York is a serious offense with serious consequences. You need an experienced New York criminal defense attorney who knows not only the law, but the science behind the testing. As I discussed in a previous blog, when one is suspected of Driving While Intoxicated but they do not submit to a chemical test such as a Breathalyzer or blood or urine test for many hours after their arrest, it is difficult, if not impossible, to determine what their Blood Alcohol Concentration (BAC) was at the time they were actually driving. As I discussed in a prior blog, in these situations, prosecutors attempt to prove the defendant’s BAC at the time of driving by Retrograde Extrapolation (RE).

To summarize, RE is a process whereby a subject’s BAC at an earlier time is determined by calculating backwards from the subject’s known BAC at a later time. However, the concept of RE (i.e., that one’s prior BAC can be determined by calculating backwards from their current BAC) is based upon some problematic assumptions. First, RE assumes that the subject is in the elimination stage. In other words, that his BAC is going down. That’s not always true. Even after one stops drinking, their BAC will continue to rise as the alcohol is absorbed into the blood stream. For example, one could drink and entire bottle of vodka and then immediately get in a car and drive 100 ft and have an accident. At the time of the accident that person’s BAC would be extremely low; the alcohol would not have had time to enter the blood stream. However, as the alcohol started, and continued, to enter the blood stream, that individual’s BAC would start to rise and would continue to rise for a while even after he stopped drinking. This is called the “absorption” stage.

An hour or more later when that individual takes a Breathalyzer, his BAC will be extremely high (considering he drank an entire bottle of vodka). A Retrograde Extrapolation analysis on that individual would incorrectly determine that his BAC at the time he was driving was even higher than when he was tested because RE is based on the assumption that the subject is in the elimination stage. This assumption is not always correct.

The only way to know if the subject’s BAC is still rising (still absorbing) or if it is falling (in other words, in the elimination stage) is to take two tests. If the second test is higher than the first test, the subject is still absorbing alcohol; if the second test is lower than the first test, the subject is eliminating alcohol. Therefore, unless two tests are done, accurate RE analysis is simply impossible. For some inexplicable reason, the New York Legislature has not found it necessary for two tests to be taken. This is puzzling since two tests would result in more accurate results. But hey, why let the truth stand in the way of a good arrest.

If you have been arrested for DWI in New York, call Tilem & Associates toll free at 1-877-377-8666 for a free consultation or visit us on the web at www.tilemlawfirm.com.