The time lapse will not help if the prosecutor and state’s expert are allowed to spoon feed retrograde analysis to jurors. Prosecutors tend to know enough about retrograde analysis to be dangerous; but they know very well that jurors can be mesmerized, bored, and duped by math and (purported) science. State’s experts often rehearse the calculation with prosecutors before trial, and testify as if the calculated blood alcohol concentration at the earlier time of driving is an absolute certainty.
An experienced defense attorney who understands the research and scientific bases (or lack of) behind retrograde extrapolation, as well as the assumptions and the factors that are / are not considered in the calculation can cast a lot of doubt on retrograde analysis -- or, even better, prevent that evidence from being admitted.
The law does not prevent a blood test 4 hours later and the State's Attorney might use retrograde extrapolation to convince a jury that you had more intoxicant in your blood while driving. Retrograde is not easy for the State's Attorney to use and an experienced DWI attorney will make it more difficult for them, perhaps impossible. There is not much out there for you to study on retrograde and the little that exists is prepared for experienced DWI attorneys and experts, so you are likely to find it more confusing than helpful. You have a case that requires a very experienced DWI attorney, so get one as soon as possible.
The State will use an expert to extrapolate if they have sufficient information to do so. The information will be derived from observations by the officer as well as statements by the offender and any witnesses. The amount of time that you had been up has no bearing on the outcome of the blood test. They will not really have a hard time making an argument that you were over the legal limit at the time of driving because the burnoff is approximately .015 per hour. If you add .015 for each of the 4 plus hours from stop to test then you well over the limit - it totals .06. Even if one assumes that you were going up at the time of stop and were not at the peak, this does not help you because of the length of delay before the test. (Most times one does not see nearly this amount of delay - perhaps an hour so that if one is over the limit at the time of the test, there is an argument to be made that one was going up at the time of stop. . .)
There are many very good lawyers who have all kinds of rabbits for blood tests. I suggest you spend some real money to hire one if you are going to fight this case.
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