Free Consultation


We’re located directly across from Vista Courthouse

Email us

Map & Directions

Pictures of attorneys Nicholas W. Christoph and William R. Christoph

Nicholas W.

William R.

Criminal Defense Experience - 40+ Years

BAC: What it is and how it can affect a DUI

We have all read at least a couple of news articles about drunk driving arrests in San Diego County. In addition to brief details of the arrest and about the person accused of DUI, the reports usually include a mention or two of BAC, the acronym for “blood alcohol concentration” (or “blood alcohol content”).

In this post, we’ll dive a little deeper than the news media does into what BAC is and how it can affect a DUI charge.

Concentrating on blood alcohol

BAC refers to the percentage of alcohol (ethyl alcohol or ethanol) that’s in a person’s bloodstream. A BAC of .10 percent means the person’s bloodstream contains one part alcohol for every 1,000 parts blood.  Drug analysis uses a different reference blood level and even with a low BAC, if a drug is involved, you may be under the influence for purposes of driving.

In California, it’s illegal to drive with a BAC of .08 percent or higher or under the influence.  According to Cal Crim Jury Instruction 2110 – Under the influence means “mental or physical abilities are so impaired that he/she  is no longer able to drive with the caution of a sober person, using ordinary care, under similar circumstances.”   you can still face arrest and DUI charges  with a BAC under .08.  There is a rebuttable presumption that a person is not under the influence under .05 BAC.

  • If you’re under 21 with a BAC of .01, you can be cited for a lesser charge and be subject to penalties that include a 1 year license suspension. if you’re driving with a BAC of .05  or above you may be charged with driving under the influence.
  • Regardless of age, if you’re on probation for a DUI conviction, it’s illegal to drive with a BAC of .01 percent or more and could face futher license suspension and probation violation consequences.
  • It’s also illegal to drive with a BAC of .04 percent or higher in a vehicle that requires a commercial driver’s license.
  • For taxicab drivers or Uber drivers – or anyone else with a passenger for hire in their vehicle – it’s unlawful to drive with a BAC of .04 percent or higher.

If you’ve been convicted of DUI for alcohol, for drugs or for both, and you had what the state terms “an excessive BAC level” (.15 percent or higher), you could receive enhanced penalties.

Another exception to the .08 percent rule

The California Department of Motor Vehicles (DMV) stresses that even though your BAC might be tested at below legal limits, that “does not mean that you are safe to drive.” If a police officer believes that you’re driving “under the influence”, you can still be arrested for DUI.

The DMV points out that alcohol affects women and men differently, and people of different weights  as well.   A woman who weighs 120 pounds can have a BAC of just .06 percent after a single drink, while a man who weighs 100 pounds more can be expected to have a BAC of .03 percent.   BAC is one of the most important criteria used in arresting, charging and resolving DUI cases, but it is not the only criteria.  Additional considerations in determining if a driver is under the influence include the manner of driving, physical abilities, field sobriety tests and mental abilities.

Top Lawyers Recognized For Excellence 2021



Member: San Diego Bar Association, North County Bar Association, American Bar Association, California Attorneys for Criminal Justice
Payment Plans: Visa, Mastercard, American Express
FindLaw Network