At Ozols Law Firm, we are often asked about breathalyzer results by those accused of drinking and driving. In order to assist our clients, we have put together an explanation of alcohol absorption rates and how it affects breath test results. If you have been charged with a DUI, call today for a free consultation.

What is alcohol and how is it processed?

Alcohol is a volatile substance meaning that it can change form a liquid to a gas and that is exactly what it does. Think about it, the breathalyzer machine is actually trying to calculate your blood alcohol level by measuring your breath. Your breath is in a gas form and with the proper ratios this calculation can be made. Alcohol is not digested immediately but instead blood moves through the lungs and some of the alcohol moves into the air sacs of the lungs. The concentration of the alcohol in the air sacs of the lungs is related to the concentration of alcohol in the bloodstream. When the alcohol from the lungs is exhaled, it can be detected by a breath testing device.

What is the absorption rate?

In a DUI trial prosecutors will often talk about “absorption rate”. They do this to try and confuse jurors and most DUI defense attorneys. The reason they can do this is because a lot of people don’t actually know how this process works. The problem is, when a defense attorney knows what they are doing, then they can turn the tables on the expert and make the expert look like an amateur. It is essential to learn the basics if you are an attorney going forward with trial or a defendant who wants to know the exact science involved in their case.

The absorption rate is how quickly the alcohol is absorbed into your body. This is used by experts to predict what your blood alcohol level was at the time of driving. It is common in a DUI trial for the breath test to be done an hour or two after the driver is pulled over. This leaves an unrealistic number on the table because the actual charge of 23152(b) says that you must be at or above a 0.08 “at the time of driving” (not hours later when the test is taken).

Absorption begins when alcohol hits the tissues in the mouth and anyone else who says otherwise is incorrect. Alcohol then passes through the tissues quickly and enters into the blood through the process of diffusion. Alcohol goes first to the stomach but then to the small intestine. Alcohol is usually absorbed 70% through the small intestine and 30% through the stomach. The small intestine has a larger surface area and a greater blood supply so once it is in there, it starts to absorb faster.

Most forensic experts do not know much about absorption and will make assumptions and estimations of how long absorption takes. I have heard from 30 minutes to 3 hours and that is absurd. The truth is, the majority of alcohol is absorbed within 15 minutes and more than 90% of alcohol is absorbed within 1 hour. With food in the stomach, complete absorption can take 2-3 hours. Again, it is important to realize what is happening here.

The prosecution will skew these numbers until they are completely in their favor. If they want to say one’s blood alcohol level was dropping, then they will say that they were fully absorbed, but if they want to say it was rising, then they will say absorption was just starting at the time the test was taken. Because alcohol is often continuously drunk throughout the night, the numbers are always changing. The peak BAC (Blood alcohol concentration) is usually around twenty to forty minutes after one’s last drink has been completed.

What rate does alcohol eliminate in the body?

People often ask questions about how alcohol is eliminated from the body. Everyone has their theories of what causes elimination, for some people it is urinating, for some drinking water, for some sleeping and for others just time. What method works best? The answer is elimination is a combination of factors in the body and it is a process that is naturally occurring. Elimination begins immediately right after the alcohol is processed and generally proceeds by two separate processes: which are excretion and metabolism.

Excretion is responsible for around 1-11% of the total amount of alcohol-removed form the body and is often by the means of breath, urine, sweat and feces. What people don’t realize is that they are actually reducing the amount of alcohol in their system just by breathing.

Metabolism accounts for 89-99% of the elimination of alcohol from the body. Metabolism occurs mostly in the liver and it is a process where the body detoxifies the substances that are affecting it negatively. The process is done by breaking down the alcohol in the system from molecules to compounds. The end process turns the alcohol into water and carbon dioxide which is excreted though the body.

The actual rate is something that is commonly disputed at trial. Again this is an area where the prosecution will often make up numbers to benefit their case. When alcohol eliminates from the body the BAC changes and that is why these calculations are so important. Alcohol rises until it hits a peak, at the peak it then stays there for a small plateau stage and then starts to be eliminated from the body and therefore drops until there is no alcohol left in the body. The height, weight, gender and body type of the individual changes the degree of elimination. A general average rate is 0.015 per hour with a normal range being between 0.01 and 0.02 per hour. The more someone drinks, the faster they would eliminate alcohol and a heavy drinker could eliminate as fast as 0.03 per hour.