Vehicle Code 23152(g) addresses situations where a driver is impaired by both alcohol and drugs simultaneously. This statute recognizes that combining substances often produces greater impairment than either alone, creating enhanced danger on California roads. Even when neither alcohol nor drug levels would independently support a DUI charge, their combined effect can result in prosecution under this subdivision.
Text of Vehicle Code 23152(g)
California Vehicle Code Section 23152(g) states:
It is unlawful for a person who is under the combined influence of any alcoholic beverage and drug to drive a vehicle.
The statute requires proof that the combination of alcohol and drugs together caused impairment, not merely that both substances were present.
Elements the Prosecution Must Prove
To obtain a conviction under VC 23152(g), the prosecution must establish each element beyond a reasonable doubt:
Element 1 – The Defendant Drove a Motor Vehicle
The prosecution must prove the defendant operated a vehicle on a public road, highway, or area accessible to vehicular traffic. Standard evidence includes officer observations, witness statements, accident reports, and circumstantial evidence of vehicle operation.
Element 2 – Under the Combined Influence of Alcohol and a Drug
The defendant must have been simultaneously affected by both alcohol and a drug (or drugs) at the time of driving. Under the combined influence means these substances together impaired the defendant’s mental or physical abilities to the degree that they could no longer drive with the caution of a sober person using ordinary care.
The prosecution must prove both substances contributed to impairment. Evidence showing only alcohol impairment should result in charges under VC 23152(a) or (b) instead. Similarly, pure drug impairment should be charged under VC 23152(f).
Understanding Synergistic Effects
The combined influence doctrine exists because mixing alcohol with drugs often produces effects greater than either substance alone. This synergistic effect makes poly-substance impairment particularly dangerous.
Alcohol and Prescription Medications
Many prescription drugs carry warnings against combining with alcohol. Opioid pain medications combined with alcohol can cause severe respiratory depression and cognitive impairment. Benzodiazepines mixed with alcohol dramatically increase sedation and impair coordination. Sleep medications and alcohol together can cause blackouts and extreme drowsiness. Even antihistamines combined with alcohol produce enhanced sedation.
Alcohol and Marijuana
Combining alcohol with cannabis produces more impairment than either alone. Studies show that even low levels of both substances together significantly degrade driving performance, including reaction time, lane-keeping ability, and decision-making.
Alcohol and Illicit Drugs
Combining alcohol with cocaine, methamphetamine, heroin, or other illegal substances creates unpredictable and dangerous impairment patterns. Stimulants may mask the sedating effects of alcohol, leading users to believe they are less impaired than they actually are.
How VC 23152(g) Cases Are Investigated
Combined influence investigations incorporate elements of both alcohol and drug DUI enforcement.
Initial Detection
Officers note standard impairment indicators including driving patterns, physical appearance, speech, balance, and behavior. The odor of alcohol combined with other symptoms suggesting drug use typically triggers further investigation.
Chemical Testing for Alcohol
Breath testing or blood testing establishes alcohol presence and concentration. A BAC below 0.08% does not preclude charges under VC 23152(g) if drugs contributed to overall impairment.
Drug Recognition Evaluation
If drug involvement is suspected, a Drug Recognition Expert may conduct a 12-step evaluation to identify drug categories involved. Physical signs such as pupil response, vital signs, and muscle tone help distinguish between substance types.
Blood Testing for Drugs
Blood samples are analyzed for both alcohol and drugs. Toxicology reports identify which substances are present and at what concentrations.
Penalties for VC 23152(g) Violations
Penalties for combined influence DUI follow the standard DUI penalty structure, though judges may view poly-substance impairment as an aggravating factor during sentencing.
First Offense
- Jail Time: 48 hours to 6 months
- Fines: $390-$1,000 plus penalty assessments (~$1,800-$2,600 total)
- License Suspension: 6 months
- Program Requirements: 3-9 month DUI school
Second Offense
- Jail Time: 96 hours to 1 year
- Fines: $390-$1,000 plus assessments
- License Suspension: 2 years
- Program Requirements: 18-30 month DUI school
Third Offense
- Jail Time: 120 days to 1 year
- Fines: $390-$1,000 plus assessments
- License Suspension: 3 years
- Program Requirements: 30-month DUI school
Fourth+ Offense (Felony)
- Jail Time: 16 months to 3 years state prison
- Fines: Up to $1,000 plus assessments
- License Suspension: 4 years
- Program Requirements: 30-month DUI school
Courts may also impose additional conditions such as drug testing, drug treatment programs, and stricter probation supervision given the multi-substance nature of the offense.
Defenses to VC 23152(g) Charges
Combined influence cases often present multiple defense opportunities because the prosecution must prove impairment from both alcohol and drugs together.
Only One Substance Caused Impairment
If evidence shows that only alcohol or only drugs caused impairment, VC 23152(g) is not the appropriate charge. The defense may argue that detected drugs did not contribute to impairment, perhaps because they were at therapeutic levels, had worn off, or were only present as inactive metabolites.
Neither Substance Caused Impairment
The defense may challenge the impairment conclusion entirely, arguing that neither alcohol nor drugs significantly affected driving ability. This is particularly viable when BAC is well below 0.08% and drug levels are low or unclear.
No Synergistic Effect
Scientific evidence may show that the particular combination of substances at the detected levels would not produce meaningful synergistic impairment. Expert toxicologist testimony can address whether the specific drug and alcohol combination would realistically cause the level of impairment alleged.
Challenging Chemical Test Results
Both alcohol and drug test results can be challenged on procedural, scientific, and constitutional grounds. Issues with blood draw procedures, sample storage, chain of custody, and laboratory protocols may affect admissibility or weight of evidence.
Challenging Field Evidence
Officer observations and field sobriety test performance can be explained by factors other than impairment. Fatigue, medical conditions, nervousness, environmental conditions, and test administration errors all provide alternative explanations.
Medical Necessity Defense
If the drugs in question were legally prescribed medications taken as directed, and the prescription was necessary for a medical condition, this context may influence how a jury views the impairment allegation, though it does not provide an automatic defense.
Practical Considerations
VC 23152(g) cases often arise when a driver’s BAC is below 0.08% but other evidence suggests impairment. Prosecutors may charge this subdivision to capture drivers who might escape conviction under per se alcohol statutes.
Common scenarios include drivers who had a drink or two while also taking prescription medications, social situations where individuals consume alcohol and marijuana together, and accidents or erratic driving with moderate BAC and drug presence.
Defendants should understand that having a legal prescription or using legal marijuana provides no protection if those substances, combined with any alcohol, impair driving ability.
Related Statutes
- VC 23152(a) – Driving under the influence of alcohol based on impairment
- VC 23152(b) – Per se DUI with BAC of 0.08% or higher
- VC 23152(f) – Driving under the influence of drugs alone
- VC 23153 – DUI causing injury, which applies when combined influence results in harm to another person
Contact a California DUI Defense Attorney
Combined influence cases require attorneys who understand both alcohol and drug impairment science. The interaction between substances adds complexity that demands experienced legal representation.
KN Law Firm defends clients facing poly-substance DUI charges throughout Los Angeles County. Contact us at (888) 950-0011 for a free consultation to discuss the specific circumstances of your case.
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