One of the fancier methods the prosecution and the law uses to determine your blood levels at the time you were driving is retrograde extrapolation. This is a mathematical calculation of what your blood alcohol levels must have been when you were driving, given its current levels. This type of calculation is often made when blood alcohol levels, at the time of testing, are lower that expected. It is used to suggest that your levels must have been higher when you were driving (your metabolism was still in the 'Absorptive Phase').
The absorptive phase is the period when the body is actively absorbing alcohol into the bloodstream. Alcohol is absorbed in the stomach, the upper intestine and the lower intestines. The rate of absorption is the highest while in the upper intestine. In about one hour, ninety percent of the alcohol will have been absorbed into the bloodstream. The rate of absorption varies considerably from individual to individual. It also will vary according to the contents of the stomach at the time drinks are ingested. Because everyone's metabolism is different and because the amount of food in your system can change the rate of absorption, retrograde extrapolation is very suspect. It is important to challenge such suppositions.
In order for the state to successfully use information gathered from blood, urine or breath testing, it must be sure the test is accurate. Blood alcohol testing is a complicated and technical chore. Because it is measuring small amounts of chemicals involved in a complicated chemical process, it is crucial for the state that the equipment be tested and calibrated frequently. It must also ensure that whoever administers the test follows all procedures exactly. This means that the person must have proper training, and if the law calls for it, re-certification at appropriate intervals. Because the test must be given under optimum conditions, the officer must arrange these conditions. There are many technical reasons why a given test could be inaccurate. If you've been charged with a DUI in San Diego call us today to schedule a consultation.