Rising Blood Alcohol as a California DUI Defense

"Rising blood alcohol" is a legal defense to California DUI charges. It is based on the theory that you weren't over the legal limit while you were driving--even though you may have been over the limit when you took a chemical DUI test.

Rising blood alcohol results from the the time it takes for your body to absorb alcohol after you have a drink. While your system is absorbing alcohol, your blood alcohol concentration (BAC) will rise steadily.

Let's say you are pulled over while driving and the officer suspects you of driving under the influence (DUI). A half-hour or more elapses between when you are pulled over and when the officer administers a DUI breath test or DUI blood test.

Your blood alcohol may have been rising in that period. So the test will show a higher BAC than you had when you actually drove.

This is why rising blood alcohol can be a powerful defense to California DUI charges.

Below, our California DUI defense attorneys answer the following frequently asked questions about "rising blood alcohol":

If, after reading this article, you would like to learn more about rising blood alcohol in California, we invite you to contact us at Shouse Law Group.

1. What is "rising blood alcohol"?

Rising blood alcohol is a simple concept. It is the result of the fact that your body takes time to absorb alcohol after you have a drink.

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 BAC steadily rises. Hence the term "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 brain and other organs.2

Alcohol is metabolized 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

a hand holding a cup of beer in a plastic cup
The way in which your body metabolizes alcohol is responsible for the phenomenon of "rising blood alcohol."

After alcohol consumption, your BAC rises rapidly and steadily--rising blood alcohol--until it reaches its maximum level.  This peak level occurs, on average, 30 minutes to an hour after you stop drinking.4 But rising blood alcohol can continue for as long as two hours, especially if you have eaten food.5

After this peak, your BAC usually begins to decline, at a more gradual rate. That is, falling blood alcohol follows rising blood alcohol. 6

This change in BAC over time--rising blood alcohol followed by falling blood alcohol--can be represented graphically as a "blood alcohol curve," as in the graph below.7 

The upward line in the graph represents the phase where your BAC is rising. 

2. Can "rising blood alcohol" lead to a false result on a California DUI chemical test?

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 (3) hours after a DUI arrest.8

If you drive while you have rising BAC, it is possible for you to be below the legal limit at the time you were driving--but over the limit by the time your BAC is tested.

To understand why, consider the following example in conjunction with the rising blood alcohol graph in Section 1 above:

Example: Carolina arrives at a party at "hour 0" in the graph. She has a drink and some snacks right away, then another drink a couple of hours into her stay at the party.

After she has been at the party for about three hours, Carolina finishes one last drink "for the road" and then gets in her car to drive home. Her house is about 10 minutes away.

At the time when Carolina gets into her car, her BAC is about .06%--below the legal limit for most drivers of 0.08% under Vehicle Code 23152(b) VC.9 Her driving ability is not impaired, and so she is not "under the influence" under Vehicle Code 23152(a) VC.10

But she makes a few driving errors while checking her smartphone. An officer pulls her over, smells alcohol on her breath and arrests her for DUI. Carolina's blood alcohol continues to rise while she is transported to the police station.

By the time she arrives there and takes a breath test, thanks to still-rising blood alcohol, her BAC is at the peak level shown in the graph above. The breath test shows Carolina to have a BAC of 0.09%--over the legal limit.

3. How can I use "rising blood alcohol" to fight California DUI charges?

It is possible to use rising blood alcohol as a legal defense to fight DUI charges.

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) VC, 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 (3) hours of your arrest.11
pair of cuffs next to a glass of whiskey and car keys
A DUI expert witness can help with creating a DUI defense strategy focused on rising blood alcohol.

This shifts the burden to you to prove that rising BAC influenced your chemical test results--and 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. If the PAS test showed a lower BAC than your later breath test, this can be strong evidence for rising BAC as a legal defense.

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's testimony about rising blood alcohol to:

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

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For more information about rising blood alcohol as a California DUI defense, 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, which is subject to error due to rising blood alcohol, detects alcohol.  
  2. MedicineNet.com, How is Alcohol Metabolized? [provides context for phenomenon of rising blood alcohol].
  3.  Alcohol Metabolism, National Institute on Alcohol Abuse and Alcoholism No. 35; PH 371 January 1997 [provides context for phenomenon of rising blood alcohol].
  4.  Forcon Forensic Consulting, Alcohol Absorption, Distribution & Elimination [provides context for phenomenon of rising blood alcohol].
  5.  Same
  6.  Same
  7.  Same
  8.  California Vehicle Code 23152(b) VC. ("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 [this presumption exists despite the phenomenon of rising blood alcohol] .")
  9. California Vehicle Code 23152(b) VC [common DUI charge to which legal defense of rising BAC can apply].  
  10.  California Vehicle Code 23152(a) VC [common DUI charge to which legal defense of rising BAC can apply]. 
  11.  California Vehicle Code 23152(b) VC, endnote 8 above.


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