Colorado DUI Defense: “Rising Blood Alcohol”

rising blood alcohol

What is rising blood alcohol?

One of the ways in which Colorado prosecutors prove drunk driving is through a DUI blood test or DUI breath test. DUI chemical tests measure the amount of alcohol present in your blood. This is known as your “BAC” – your blood alcohol concentration or blood alcohol content.

But there is a delay between when you drink and when the alcohol becomes detectible in your blood. As a result, you might not be legally intoxicated when you are pulled over. Yet, by the time you take a chemical test, you might be over Colorado's absolute BAC limit of .08% for a Colorado DUI “per se”. And even if you are still below the limit, the difference might be enough to persuade a jury you couldn't drive safely.

Like all the best Colorado DUI defense lawyers, we understand the science behind rising blood alcohol levels. We invite you to contact our caring DUI attorneys for a free consultation to find out if your blood level was on the rise when you were arrested for:

  • Colorado DUI, 
  • Colorado DUI “per se”,
  • Colorado DWAI, 
  • Colorado UDD, or another 
  • Colorado drunk driving offense.

In this article, our top Denver DUI attorneys explain:

1. How your system absorbs alcohol

When you drink, most of the alcohol is absorbed in your digestive tract. From there, it passes into your blood. Some of the alcohol is excreted in your breath and urine. The rest is carried to your various organs, including your brain and your liver.1

The liver metabolizes alcohol so that your system can eliminate it. But it can only detoxify a certain amount of alcohol at a time. Until it can complete the process, some of the alcohol remains in your blood.2This is known as your blood alcohol concentration or blood alcohol content (“BAC”).

When you consume alcohol, your BAC rises rapidly and steadily until it reaches its maximum level or "peak." This is where the term “rising blood alcohol” comes from.

BAC peaks on average between 30 minutes and an hour after you stop drinking. But it can take longer -- up to two hours. The precise time varies from person to person and even within the same person, depending on the given day and circumstances.3

Factors that affect the rate of alcohol absorption include:

  • Your physical state,
  • Your weight,
  • Your gender,
  • Whether (and how much) you have eaten, and
  • The presence of other substances in your system.

After you stop drinking, your liver eventually catches up. More alcohol is eliminated and less is absorbed. Your BAC then starts to fall at a more gradual rate.

2. Rising blood alcohol and DUI chemical tests

Colorado DUI blood tests are not given right when you are pulled over. Usually the officer will question you first. You may be asked to take a preliminary breath test or other roadside sobriety tests before you are arrested. Only then are you taken to a police station or other facility to have a post-arrest DUI chemical test.

In Colorado DUI chemical tests must be given within two hours of driving.4For some people, however, their BAC may still be “on the rise.” As a result, it is possible for you to be legally capable of driving at the time you are pulled over, but over the limit by the time your blood is drawn.

Imagine, for example, this scenario:

You go out to a restaurant. When you arrive, you have a drink and some snacks at the bar while you wait for your table. You finish your first drink and order a second one.

If you stay and drink it normally, after about 45 minutes your BAC might well exceed .08% -- Colorado's legal DUI “per se” limit.

But what if instead you get tired of waiting? When drink #2 comes you bolt it down and leave for another restaurant a few blocks away.

The alcohol from the second drink has not yet fully entered your bloodstream. Your BAC could well be in the “gray” area of at least .05% but still less than .08%. This might be enough to make you guilty of driving while ability impaired (Colorado DWAI). But it would not be enough for a “per se” DUI.

Yet your BAC would still be rising. If you were pulled over for a traffic violation, the officer might smell the alcohol on your breath and arrest you. And by the time your blood was taken, you could well be over the absolute legal limit of .08%.—even though you weren't drunk at the time you drove.

3. How do I prove my blood alcohol was on the rise?

A forensic toxicologist or other expert witness can look at your Colorado DUI chemical tests and other evidence. He or she will use this evidence to establish your personal BAC timeline.

If the DUI defense expert determines that your BAC was on the rise at the time of your arrest, your experienced Colorado DUI lawyer may be able to get the charges against you dropped. Or we can use it to negotiate a plea bargain to a reduced charge that will let you keep your Colorado driver license.

And if your case does go to trial, your DUI criminal defense attorney can use the evidence to counter the prosecution's expert witness. At the very least, we may be able create reasonable doubt for the jury that you were over the legal limit at the time you drove.

Call us for help…

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There is no one-size-fits-all defense for Colorado DUI or DWAI. The best Colorado drunk driving defense is the one that works for you.

If you or someone you know has been arrested on a Colorado drunk driving charge, we invite you to contact us. We offer free consultations in person or by phone or.

You can reach us most quickly by using the form on this page. We will get back to you promptly to discuss your case and figure out the best legal defense for your situation.

Or you can contact our Denver DUI defense office at:

Colorado Legal Defense Group
1400 16th Street
16 Market Square
Denver CO 80202
(720) 955-6112


Legal references:

  1. MedicineNet.com, How is Alcohol Metabolized?Brown University Health Education, Alcohol and Your Body.
  2. Alcohol Metabolism, National Institute on Alcohol Abuse and Alcoholism No. 35; PH 371 January 1997.
  3. Forcon Forensic Consulting, Alcohol Absorption, Distribution & Elimination.
  4. 42-2-126, C.R.S.; 42-4-1301, C.R.S.

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