Rising Blood Alcohol as a California DUI Defense

DUI charges almost always result from chemical test results that show a driver “over the legal limit.”

But chemical tests don't always paint an accurate picture. One reason is “rising blood alcohol.”

What is rising blood alcohol?

After you have a drink, it takes from 30 minutes to two hours for the alcohol to be fully absorbed by your system. As your system absorbs the alcohol, your blood alcohol content (BAC) steadily rises

California DUI laws make it unlawful to be “under the influence” while driving.  But DUI chemical tests by their very nature are not given until after you have stopped driving.

If your blood alcohol level is “on the rise” at the time you are pulled over, it might rise even further before your chemical test.  When this happens, the test will show a higher BAC than you had when you actually drove.

Rising blood alcohol is a scientific fact. But law enforcement and prosecutors often ignore the science. As a result, thousands of innocent people are wrongfully charged every year with California DUI.

To help you understand the nuances of the “rising blood alcohol” defense, our DUI defense attorneys discuss the following, below.

  1. Alcohol absorption and “rising blood alcohol”
  2. Rising blood alcohol and DUI chemical tests
  3. Proving “rising blood alcohol”

If after reading this article you would like more information, we invite you to contact us at Shouse Law Group.

You may also find helpful information in our related articles on Driving Under the Influence; Vehicle Code 23152(a); Vehicle Code 23152(b); Understanding Your Blood Alcohol Concentration (BAC); Field Sobriety Tests (FSTs); DUI Breath Testing Errors; DUI Blood Testing Errors; DUI of Drugs; Top 10 Defenses in a California DUI Case; 20 Ways to Beat a California DUI; The Probable Cause Required to Initiate a DUI Investigation; Miranda Rights; California Title 17 Procedures; DUI Causing Injury; DUI Probation; DMV Driver's License Suspensions; California DUI School; California DUI Penalties; Refusing to Submit to a DUI Chemical Blood or Breath Test; Health and Safety Code 11550, California's "Being" Under the Influence Law; California DUI Charges for Minors Under 21; and The 10 Phases of a DUI Case.

1. Alcohol absorption and “rising blood alcohol”

When you consume alcohol, most of it is absorbed in your stomach and small intestine.1 From there, it passes into your blood and on to your various organs, including the brain.2

Alcohol is metabolized (detoxified) by the liver and then eliminated.  But the liver can only metabolize so much alcohol at one time.  Whatever it can't metabolize remains in the blood until the liver catches up.3 This is your blood alcohol content (BAC).

After alcohol consumption, your BAC rises rapidly and steadily until it reaches its maximum level.  This peak level occurs, on average, between half-an-hour to an hour after you stop drinking.4 But it can take as long two hours to reach a peak level, especially if you have eaten food.5

After you stop drinking, elimination eventually catches up with absorption.  At this point, your BAC usually begins to decline, at a more gradual rate.6

This change in BAC over time can be represented graphically as a "blood alcohol curve."7 Absorption is represented by a rising line and elimination by a falling one.

The upward line in the graph represents the phase in which your blood alcohol is “on the rise.” When your blood alcohol level is rising, your BAC increases with the passage of time.

2. Rising blood alcohol and DUI chemical tests

Chemical tests are not always given immediately after you are pulled over. Often, they are not performed until after you have been arrested and taken to the police station.  Nevertheless, a chemical test result is considered valid as long as the test was given within three hours after a DUI arrest.8

If you drive while your BAC is in the rising phase, it is possible for you to be below the legal limit at the time of driving… but over the limit by the time your BAC is tested.

To understand why, take a look at the graph in Section 1, above.

Assume the graph represents your drinking at a party.  You arrive at hour “0” and have a drink and some snacks right away.

If you keep drinking, you will be over California's strict legal limit of .08% BAC about 45 minutes after you finish drink #2.  Having a third drink will keep your BAC above the legal limit for a period of well over three hours (approximately hours 2 ¼ through 6 on the graph).

But… let's say that instead of sticking around, you decide to leave the party after you've been there about two hours. You throw back “one for the road” (drink #2) and immediately leave for home, a 10-minute drive away.

At this point, your BAC is about .06%. You may or may not actually be impaired and, hence, in violation of California Vehicle Code 23152(a).9 But either way, you are still below the absolute California legal limit of .08% (the “per se” limit) set forth in California Vehicle Code 23152(b).10

If you get pulled over and arrested now, however, by the time you get to the station and take a chemical test, your BAC might well be .08% or more.  And even if you are not over this limit, the increase in BAC might be enough to convince a jury that you were actually impaired.

Proving you had “rising blood alcohol” is one way you might beat the charges.

3. Proving “rising blood alcohol”

Establishing a defense of rising blood alcohol almost always requires the testimony of a DUI defense expert witness. This is because a DUI chemical test is considered accurate until proven otherwise.

Under California Vehicle Code 23152(b), it is a rebuttable presumption that you were driving with a BAC over the legal limit if:

  • A chemical test registered a BAC of .08% or greater, AND
  • The test was administered within three hours of your arrest.11

This shifts the burden to you to prove that your BAC was under the legal limit at the time you drove.

An expert witness – usually a forensic toxicologist – will establish your personal BAC timeline. It will take into account all the applicable and relevant factors -- including a preliminary alcohol screening (PAS) breath test if you took one.12

Often, a DUI defense expert is able to provide convincing evidence of rising blood alcohol before a case ever goes to trial. When this happens, an experienced DUI attorney can often negotiate to get the charges thrown out… or, at the very least, reduced to a lesser charge.

But even if your case goes to trial, an experienced defense attorney can use a DUI defense expert to:

  • Discredit the prosecution's expert witness, and
  • Establish reasonable doubt that you were over the legal limit at the time you drove.

Call us for help...

For more information about California's DUI laws, or to discuss your case confidentially with one of our criminal defense attorneys, please don't hesitate to contact us at Shouse Law Group. Our California criminal law offices are located in and around Los Angeles, Orange County, San Diego, Riverside, San Bernardino, Ventura, San Jose, Oakland, the San Francisco Bay area, and several nearby cities. For information about rising blood alcohol in Nevada, see our article about rising blood alcohol in Nevada.

Legal references:

1 A small amount of alcohol is excreted through breath, saliva, sweat and urine. This is how a DUI breath test detects alcohol.  For more information, see California DUI Breath Testing is Subject to a Wide Variety of Errors.

2 MedicineNet.com, How is Alcohol Metabolized?

See also, Brown University Health Education, Alcohol and Your Body.

3 Alcohol Metabolism, National Institute on Alcohol Abuse and Alcoholism No. 35; PH 371 January 1997.

4 Forcon Forensic Consulting, Alcohol Absorption, Distribution & Elimination.

5 Same

6 Same

7 Same

8 California Vehicle Code 23152(b) …In any prosecution under this subdivision, it is a rebuttable presumption that the person had 0.08 percent or more, by weight, of alcohol in his or her blood at the time of driving the vehicle if the person had 0.08 percent or more, by weight, of alcohol in his or her blood at the time of the performance of a chemical test within three hours after the driving.

9 California Vehicle Code 23152(a).  It is unlawful for a person who is under the influence of any alcoholic beverage to drive a vehicle.

10 California Vehicle Code (b).  It is unlawful for a person who has 0.08 percent or more, by weight, of alcohol in his or her blood to drive a vehicle…

11 California Vehicle Code 23152(b), endnote 8.

12 You are not obligated to take a PAS test unless you are under 21 [Vehicle Code 23136(a)] or on probation for a prior DUI [Vehicle Code 23154(a)].  But if you did take one and it showed a BAC lower than your post-arrest chemical test, this can be strong evidence that of rising blood alcohol.

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