If a person is pulled over by the police for driving under the influence1 and their body is still absorbing alcohol when they are given a breathalyzer test, the person’s blood alcohol content (BAC) will not accurately show their BAC at the time when they were driving.
This is sometimes known as the “rising blood alcohol defense.”
The rising blood alcohol defense is based on the fact that alcohol takes time to be absorbed into a person’s blood stream.
Depending upon what foods a person has eaten and what kinds of drinks they have had, it can take up to 2 hours for alcohol to enter a person’s bloodstream and reach the peak absorption level.
Impact Of Food On Alcohol Absorption
- Empty Stomach
- Full Stomach
This means that if a person drinks right before they drive a short distance, the alcohol that they drank probably hasn’t entered their blood stream until after they finish driving2.
General Alcohol Concentration Curve
- Y: Alcohol Concentration
Male v. Female Alcohol Absorption Rates.
Women generally have less body water than men and this means that a woman’s BAC may rise higher than a man’s more quickly because a woman has less body fluid to dilute the alcohol than a man does3.
If a suspect is stopped and suspected of DUI and the PAS is given 15 or 20 minutes later with a result of 0.08%, the person will be arrested for DUI and then asked to submit to chemical testing4.
What if The Second BAC Result is Higher?
If the second test is 0.12%, then the person’s BAC was on the rise.
A defense attorney can argue, however, that the defendant stopped drinking 30-minutes before being stopped and if the individual’s BAC was 0.08% according to the PAS result, then his BAC must have been under 0.08% at the time he was driving.
How do Prosecutors Determine BAC at the Time of Driving?
Prosecutors will use retrograde extrapolation to attempt to determine BAC at the time of driving.
You can use our calculator below to see what the prosecution may determine your BAC was at the time of driving.
Try our Retrograde Extrapolation Calculator To Estimate Your BAC at the Time of Driving
When you drink, your BAC is either rising or falling so that when you are driving, your BAC could have been lower than 0.08%.
Any alcohol you drink is absorbed through the walls of your stomach and small intestine. While being absorbed, your BAC will be rising. When you cease drinking, absorption stops and your BAC will peak before beginning to fall.
1) What do absorption times have to do with the rising blood alcohol defense?
The peak absorption level is when alcohol gets into a person’s bloodstream.
The time that it takes for alcohol to enter someone’s blood can be affected by whether they were drinking on an empty stomach or whether they had any food present in their stomach when they were drinking.
A person’s BAC will generally rise as more alcohol goes into their bloodstream, so their BAC may actually have been lower when they were driving than what a breathalyzer machine show it to be later on.
2) How can a DUI attorney prove someone’s blood alcohol level was rising?
An experienced DUI attorney can help prove your blood alcohol level was rising by hiring a toxicology expert to show that your BAC was actually lower than 0.08% when the police initially stopped you for DUI.
3) What kinds of evidence could a person use to prove that their blood alcohol content was rising when they took a breathalyzer test?
A person who has been arrested for DUI may need to use evidence such as receipts from a restaurant or bar that show what foods they ate and what drinks they had before driving if they want to use the rising blood alcohol defense.
Also, eyewitness testimony that can show that the person was sober when they started driving may be helpful.
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“The way that alcohol is processed through your body is like a bell-shaped curve. That means that when you consume the alcohol, it needs to be absorbed into your system, distributed through your system, and ultimately eliminated. So your blood alcohol concentration will rise, plateau, and then go down.
Rising blood alcohol defense is a really important tool in DUI defense.
Because they can’t test your blood alcohol concentration at the time of driving. They can only test your blood alcohol concentration at the time of arrest, or after that point. So they need to estimate what your blood alcohol concentration was at the time of driving. And if you just finished drinking before getting into the car and driving, and you were pulled over, and a period of time went by where you are absorbing alcohol, by the time you took the test, you may have had a much higher blood alcohol concentration than you did at the time of driving. So it’s important to understand how rising blood alcohol concentration works, how the scientific formulas that law enforcement uses are applied to your case, and how to debunk their theories in proving your blood alcohol concentration. I have a client who was arrested and charged with DUI. He finished drinking five minutes before getting into his car and driving. From the time of driving to the time of the test was two hours. That means that his body had plenty of time to absorb, distribute, and then begin eliminating alcohol from the time of driving to the time of the test. That means that we have no idea what his blood alcohol concentration was at the time of driving. And what’s really important is that everybody absorbs alcohol and a different rate. So I was able to convince the prosecutors that because such a lengthy amount of time had passed between the time of driving and the time of the test, and because my client had finished drinking immediately before driving, there was no way to use his blood alcohol concentration that he registered of the test against him in his criminal case. As a former DUI prosecutor, I’ve handled thousands of these types of cases. I know how to apply the rising blood alcohol defense. I understand the different scientific formulas that the experts use in applying their calculations to determine what your blood alcohol concentration was at the time of driving. I understand that lot of assumptions are made with respect to your behavior in determining what your blood alcohol concentration was at the time of driving. Because of my experience, I’m able to convince prosecutors not to file charges against you or, in the alternative, to reduce the charges that have already been filed against you if the situation warrants it. Give me a call. I can help.”
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- California Vehicle Code 23152(a): “It is unlawful for a person who is under the influence of any alcoholic beverage to drive a vehicle.” [↩]
- See: Absorption and Peak Blood Alcohol Concentration After Drinking Beer, Wine, or Spirits. [↩]
- See gender differences in moderate drinking effects: See Also Kwo, P.Y.; Ramchandani, V.A.; O’Connor, S.; et al. Gender differences in alcohol metabolism: Relationship to liver volume and effect of adjusting for body mass. Gastroenterology115(6):1552-1557, 1998 [↩]
- Vehicle Code 23152(b) VC: “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. [↩]