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Introduction
Most drivers are familiar with the idea that a Blood Alcohol Content (BAC) of 0.08% is the legal threshold for DUI in California. But a common question many ask is: Can you still be charged with a DUI if your BAC is below that limit? The answer is yes—under certain conditions.
In California, DUI laws don’t rely solely on a numeric BAC level. While reaching or exceeding 0.08% often results in an automatic DUI charge (called DUI per se), you can still be charged with DUI even if your BAC is lower, as long as there’s enough evidence that you were impaired while driving.
This article breaks down how DUI laws in California apply to drivers with BACs below the legal limit, what types of evidence law enforcement can use to support those charges, and what “impairment” actually means under the law. We’ll also cover key scenarios where a lower BAC can still result in arrest and prosecution, especially for specific categories of drivers.
Understanding the Legal BAC Limit in California
In California, the standard legal BAC limit is 0.08% for adult drivers operating non-commercial vehicles. This threshold is used by law enforcement and the courts to establish DUI per se—meaning the BAC number alone is enough to charge someone with driving under the influence.
However, the law also allows for DUI charges based on observed impairment, regardless of BAC. This means that a driver with a BAC of 0.05%, for example, could still face DUI charges if they show signs of being under the influence while driving.
In addition to the 0.08% limit for most adults, California has lower thresholds for specific groups:
- 0.04% for commercial vehicle drivers
- 0.01% for drivers under 21 (zero tolerance policy)
These thresholds represent the maximum BAC levels allowed by law for each group, but impairment-based charges can still apply at any level if there’s supporting evidence.
What Is Considered “Impaired” Below the Legal Limit?
Impairment refers to any level of alcohol or drug influence that affects a person’s ability to drive safely. In California, even if your BAC is under the legal limit, you can be considered impaired if your driving behavior shows reduced judgment, coordination, or reaction time.
Law enforcement looks for several signs to assess impairment during a traffic stop, including:
- Swerving or weaving between lanes
- Slow or erratic driving
- Failing field sobriety tests
- Bloodshot eyes or slurred speech
- Alcohol odor on breath
If these indicators are present, and the officer believes you’re unable to operate a vehicle safely, you may be arrested—even if your BAC is below 0.08%.
California Vehicle Code § 23152(a) states that it is unlawful for a person who is under the influence of alcohol to drive a vehicle, regardless of their BAC level. This section is often used to support DUI charges in cases where the BAC is low but signs of impairment are clearly documented.
Scenarios Where You Can Get a DUI Below 0.08%
Several real-world scenarios can lead to a DUI charge in California even when the driver’s BAC is under the legal limit:
1. Observable Impairment with Low BAC
If you fail a field sobriety test, drive unsafely, or appear visibly intoxicated, officers can arrest you based on observed behavior—even if your BAC is 0.05% or lower.
2. Drug or Medication Influence
You can be charged with DUI if you’re impaired due to drugs or prescription medications, even without any alcohol in your system. California law treats drug impairment the same as alcohol impairment.
3. Underage Drivers
For drivers under 21, a BAC of 0.01% or higher violates the state’s zero tolerance laws. DUI-related penalties can be applied even without proof of significant impairment.
4. Commercial Drivers
A commercial driver operating a vehicle with a BAC of 0.04% or higher may be subject to DUI penalties under stricter commercial driving laws.
5. Combined Substance Use
Even if your BAC is low, using alcohol in combination with other substances—such as cannabis or prescription medication—can result in observable impairment and DUI charges.
These scenarios show that California’s DUI laws are not solely tied to numbers; they also consider a driver’s actual behavior and ability to drive safely.
How Law Enforcement Determines Impairment
When an officer suspects DUI, they will conduct a traffic stop and evaluation process that includes several stages:
- Observation: The officer watches your driving before stopping you. Swerving, speeding, or erratic behavior may prompt a stop.
- Initial Interaction: Officers assess physical signs like slurred speech, odor of alcohol, or confusion.
- Field Sobriety Tests: These include walking in a straight line, standing on one leg, and other coordination checks.
- Preliminary Breath Test: This roadside breathalyzer gives a rough estimate of BAC.
- Chemical Testing: If arrested, you’ll be required to take a formal breath, blood, or urine test.
If you show clear signs of being impaired—even with a BAC under 0.08%—you can still be charged under California Vehicle Code § 23152(a).
Impairment doesn’t need to be extreme or obvious; even subtle signs can support a DUI charge if law enforcement believes they affect your ability to drive safely.
Does BAC Always Need to Be Over the Limit for a DUI Charge?
No. BAC does not always need to exceed the legal limit for a DUI charge to occur in California. In fact, the law specifically allows for DUI charges based solely on impairment—regardless of your exact BAC level.
Here’s a breakdown:
- BAC ≥ 0.08%: You can be charged under Vehicle Code § 23152(b), which focuses on the numeric threshold.
- BAC < 0.08%: You can still be charged under Vehicle Code § 23152(a), based on impairment alone.
In practice, this means that a driver with a 0.06% BAC who shows signs of erratic driving or fails sobriety tests may still face a DUI charge. The key factor is whether the driver was under the influence to a degree that affects safe driving.
This flexible approach gives law enforcement discretion in enforcing DUI laws, ensuring that dangerous driving behavior can be addressed even when alcohol levels are low.
Can Prescription Drugs or Marijuana Lead to a DUI Below the Legal Limit?
Yes. California law makes it clear that any substance that impairs your ability to drive—whether alcohol, prescription medication, or marijuana—can be grounds for a DUI charge.
For example:
- Prescription medications like painkillers, sleep aids, or anti-anxiety drugs can impair alertness and reaction time.
- Cannabis use can cause delayed responses and poor judgment, even in small amounts.
- Over-the-counter drugs like allergy medications may also cause drowsiness or disorientation.
These substances often do not affect BAC, meaning your breath or blood test may show a level below 0.08% or even zero—but you can still be charged based on observed impairment.
This is especially important in California, where recreational marijuana is legal but still subject to DUI enforcement. Drivers are responsible for ensuring they are not impaired, regardless of the legality of the substance.
FAQ
Can you be arrested for DUI with a BAC of 0.06%?
Yes. If you show signs of impairment, you can be charged under California law even with a BAC below 0.08%.
Is BAC the only factor in DUI cases?
No. Law enforcement can base charges on observable impairment, field sobriety tests, and behavior.
Does marijuana affect BAC?
No. Marijuana does not raise BAC, but it can still impair driving and lead to DUI charges.
What law covers impairment-based DUI in California?
California Vehicle Code § 23152(a) allows for DUI charges based on impairment, regardless of BAC.
Do commercial drivers face stricter BAC rules?
Yes. The legal limit is 0.04% for commercial drivers in California.
What happens if you’re under 21 with a low BAC?
California’s zero tolerance law sets the limit at 0.01% for drivers under 21, with automatic penalties for any alcohol detected.
Can a combination of substances lead to DUI?
Yes. Using alcohol with other substances—even at low levels—can result in impairment and charges.
Conclusion
In California, a DUI charge isn’t limited to drivers who exceed the 0.08% BAC limit. If law enforcement believes your ability to operate a vehicle is impaired, you can face DUI charges—even with a BAC below the legal threshold.
Whether due to alcohol, drugs, or a combination of both, the key issue is impairment behind the wheel. Knowing this helps drivers understand that “under the limit” doesn’t always mean “under the law.”
For a full explanation of BAC limits and DUI enforcement, visit the Blood Alcohol Content And Legal Limits pillar page. To better understand how BAC is measured and interpreted, explore the mini-hub: What Blood Alcohol Content (BAC) Means Under DUI Laws.