How Alcohol Interacts with the Human Body
It is important to understand how alcohol interacts with the human body when discussing a Missouri DUI / DWI case.
Lay people assume that if you “blew above 0.08% BAC,” your case is hopeless. Testing above the legal limit, by itself, is only an indicator of intoxication, it does not indicate “when” the intoxication took place. More specifically, it does not indicate that what you are blowing at the time of the chemical test is at all indicative of what you would have blown at the time you were driving a car sometime earlier in the evening.
Under RSMo. 577.037.1, evidence that your BAC was at or above 0.08% is evidence that you were intoxicated AT THE TIME THE CHEMICAL TEST WAS TAKEN in a Missouri DUI / DWI case.
It is not conclusive at all to the notion that you were intoxicated AT THE TIME YOU WERE OPERATING YOUR VEHICLE. You see, it is not how much you drank. That is the big misconception. It is how quickly did the alcohol you consumed “absorb” into your system.
Four beers on an empty stomach will go straight into your system and quickly become a predictable BAC. The same four beers on a full stomach will take longer to hit your bloodstream, resulting in a lower BAC for a longer period of time, and a higher BAC at a later time. So even though you ultimately will "get to" the same BAC, it will take a longer or shorter amount of time to do so based on what it is in your system.
So, if you drank on a full stomach, you can often show that your BAC at the time you were observed operating your vehicle was under the legal limit of 0.08%, and that it only rose above 0.08% much later when you gave your breath test due to a full stomach, or other factors. This is called the "Rising BAC" defense, and it is a good one.
The presumption in RSMo. 577.037 is clear: the presumption of a 0.08% indicating you are intoxicated only applies to the time the test is given. Frankly, this is largely irrelevant.
The only important thing is what your BAC was when you were driving. This is particularly helpful in the civil portion of your Missouri DUI / DWI case (where the Missouri Director of Revenue is trying to take your driver's license away), because if they cannot show you were above 0.08% BAC AT THE TIME YOU WERE DRIVING, NOT AT THE TIME OF TESTING, you win. (Note: you can be convicted of DUI / DWI in the criminal portion of your case at BACs below 0.08%).
Alcohol Absorption
When you consume alcohol, it is absorbed into your bloodstream by diffusion through the various mucous membranes in your body. Absorbed alcohol is alcohol that has made its way to your bloodstream, and the rest of your body.
Alcohol absorption is the process of consumed alcohol getting into your bloodstream. Absorption can occur through your mouth, your throat and your gastrointestinal tract. Different stomachs empty at different rates, often depending on what the person had to eat as well as drink.
When you have an empty stomach, the pyloric valve at the base of your stomach is open, and absorption of the alcohol into your bloodstream will occur more quickly. However, when you have a full stomach, the pyloric valve at the base of your stomach is closed. Alcohol absorption in your body will occur even with the pyloric valve closed through the lining of your stomach and through your small intestine, but at a much slower rate.
How quickly your stomach valve opens up largely determines how quickly full absorption of the alcohol will occur into your bloodstream. Until your body fully absorbs any consumed alcohol in the absorptive phase, your breath alcohol level will be higher than the actual blood alcohol level in your body.
Accordingly, when you are in the “absorptive phase” you will give an artificially high breath sample that is not indicative of your true BAC, but believe me, the State of Missouri will attempt to use ANY breath test above 0.08% as a valid indicator of your BAC at the time you were driving.
Nearly 90% of consumed alcohol is absorbed into your body within 1 hour, and nearly all alcohol within 1.5 hours, although 3 hours may be required for complete absorption in some individuals.
Many factors have to be taken into consideration in calculating how quickly you will fully absorb alcohol: your body weight, your sex, your general health, your body fat content, your metabolism, the quantity of food in your stomach, when you last ate, the type of food you ate, the amount of alcohol you consumed, the type of alcohol you consumed (percentage by volume), when your drinking began, when your drinking stopped, and your overall, alcohol consumption history.
The main point is, until the alcohol is absorbed in various ways by your body, if you were given a breath test during this absorption phase, an artificially high breath test reading will occur, as your actual blood alcohol content (which of course no one is bothered to actually measure at any time) is lower than what the breath testing machine is claiming it is at the time of the test not at the time you were driving.
You should be aware that you have the right to remain silent—exercise it!
When you are read your Miranda warning at the station, they will ask you what you had to eat, what you had to drink, if you are “under the influence,” etc.
Don't answer any questions, even if they look harmless on their face. If they are asking it, they intend to use the information against you later.
Alcohol Distribution
Once alcohol is absorbed in your body through your bloodstream in a Missouri DUI / DWI case, it is distributed through your body until it is eliminated.
The distribution generally goes from your mouth to throat to esophagus to stomach to small intestine to portal vein to liver to right side of the heart to lungs to left side of the heart into the blood into the extremities (including the brain) to portal vein with re-circulation through the liver continuing until elimination.
Alcohol Elimination
Alcohol is eliminated from your blood, mostly by your liver, through metabolism, excretion, and evaporation. During the alcohol elimination phase, your blood alcohol content will be higher than your breath alcohol content.
Your breath alcohol concentration is higher than blood alcohol concentration while the alcohol is being absorbed, and then the inverse is true once the alcohol is in your bloodstream and being distributed/eliminated by your body. Alcohol tolerance in alcoholics drastically affects the “burn off” of alcohol or the actual alcohol elimination rate.
As discussed above, a BAC result on a breath test will only be evidence of your intoxication level at the time you gave a breath test, not at the time you were actually driving. To overcome this, the state will often have a toxicologist as a witness that will perform what is called “retrograde extrapolation.”
An expert utilizing “retrograde extrapolation” will attempt to guess what your BAC might have been at the time you were driving based on the number of drinks, when you stopped drinking, what you ate, and the amount of time between when you were stopped and when you gave the breath test after you were arrested.
Of course, there is conjecture and speculation—but it is often enough to convict you or suspend your driver's license. Even assuming the information is 100% accurate the expert is plugging into the equation (and of course it can't be) retrograde extrapolation cannot give a specific BAC at the time you were driving—only a guess.
It is the least effective in determining your BAC where you are in the absorptive phase at the time you were arrested (i.e.—you have drinks for the road on a full stomach, delaying the alcohol absorption, you are stopped, arrested, and then breath tested sometime later at the time the alcohol is then hitting your bloodstream after driving—giving good evidence that you were below 0.08% BAC in many cases at the time you were driving).