What Constitutes “Driving Under the Influence” in California Beyond BAC?

Most people in Redlands believe that if they stay under the 0.08 percent limit, they are safe from a DUI arrest. This dangerous misconception leads many good people into the San Bernardino County court system. In California, the law does not just care about the number on a breathalyzer. If the police believe your physical or mental abilities are impaired, they will arrest you regardless of your blood alcohol concentration (BAC). Understanding what constitutes “driving under the influence” in California beyond BAC is the only way to recognize the true scope of the state’s power. We have spent years fighting these cases because we know that a low chemical test result does not mean the prosecution will simply give up.

The Subjective Standard of Vehicle Code 23152(a)

California law divides a standard DUI into two main parts. While Vehicle Code 23152(b) focuses on the 0.08 percent limit, Vehicle Code 23152(a) is much broader (leginfo.legislature.ca.gov). This statute makes it unlawful to drive while under the influence of any alcoholic beverage.

The legal definition of “under the influence” is not tied to a specific number. According to the California Jury Instructions (CALCRIM 2110), a person is under the influence if their mental or physical abilities are so impaired that they can no longer drive with the caution of a sober person. This is a subjective standard. If a Redlands Police Department officer sees you swerving on Brookside Avenue or failing to maintain your lane on the I-10, they can arrest you for a DUI even if you blow a 0.05 percent.

The prosecution uses your driving pattern and physical symptoms to build this case. They will point to slurred speech, watery eyes, or an unsteady gait as “proof” of impairment. We know how to attack these observations because many of these symptoms have perfectly legal explanations; fatigue, allergies, or the stress of being pulled over can all mimic intoxication.

Driving Under the Influence of Drugs (DUID)

In 2026, we are seeing a massive surge in drug-related DUI arrests. Under Vehicle Code 23152(f), it is illegal to drive while under the influence of any drug. Unlike alcohol, there is no “per se” limit for drugs in California. There is no legal amount of marijuana, cocaine, or even prescription medication that allows you to drive if it impairs your ability to operate the vehicle.

The definition of a drug for DUI purposes is extremely broad. It includes:

• Illegal narcotics like methamphetamine or heroin
• Prescription medications like Vicodin, Xanax, or Ambien
• Over-the-counter medicines like Benadryl or certain cough syrups
• Marijuana, even if you have a medical recommendation or use it recreationally

The state does not have to prove that the drug is illegal. They only have to prove that it “appreciably impaired” your nervous system, muscles, or brain. We often see cases where people are arrested for taking their prescribed medication exactly as directed by their doctor. The law says having a prescription is not a defense if that drug made you unsafe to drive. We fight these charges by bringing in our own forensic toxicology education to show that the mere presence of a drug in your system does not equal impairment at the time of driving.

The Danger of Combined Influence

Perhaps the most aggressive charge the prosecution can file is under Vehicle Code 23152(g). This statute covers driving under the combined influence of alcohol and drugs. This is a common trap for Redlands residents who might have a single glass of wine with dinner while also taking a common prescription for anxiety or pain.

Separately, neither the alcohol nor the medication might be enough to impair a person. But the prosecution will argue that the two substances worked together to create a “synergistic effect.” They claim the combination makes the impairment much worse than the substances would on their own. This charge is particularly difficult to fight without a legal team that understands the complex science behind drug interactions. We scrutinize the toxicology reports to challenge the government’s theory that these substances actually caused you to drive unsafely.

How Police Prove Impairment Without a High BAC

Since there is no “legal limit” for most drugs or for subjective alcohol impairment, the police rely on different tools. If your BAC is low but you still seem “off,” the officer will likely call for a Drug Recognition Expert (DRE).

A DRE is an officer who has received additional training to identify drug impairment. 

They follow a 12-step evaluation process (nhtsa.gov) that includes:

• Checking your pulse and blood pressure
• Examining your pupil size and reaction to light
• Performing the “Romberg Balance” test
• Looking for injection sites or other physical signs of drug use

Many people think the DRE’s opinion is a scientific fact. It is not. It is an opinion based on a checklist that is often administered in poor lighting or in high-stress environments, such as the side of a busy Redlands road. We have won cases by exposing the flaws in the DRE’s evaluation. We show that the officer’s “expert” opinion was, in fact, a series of guesses influenced by their desire to make an arrest.

Local Enforcement and the San Bernardino Superior Court

If the Redlands Police or the California Highway Patrol (CHP) arrest you, your case will likely be filed in the San Bernardino Superior Court. This court system is one of the busiest in the state, and the prosecutors here are aggressive. They do not need a breathalyzer result to press for a conviction.

In Redlands, we see many DUI stops near the University of Redlands or along the Orange Street shopping centers. Often, these stops are based on minor equipment violations, like a broken taillight, which then spiral into full DUI investigations. If the officer smells alcohol or notices a pill bottle in your cup holder, the investigation begins. We look at every detail of that stop. If the officer lacked reasonable suspicion to pull you over in the first place, we can move to have the evidence suppressed, which often leads to the dismissal of the entire case.

Penalties for DUIs Beyond BAC

Do not be fooled into thinking that a “drug DUI” or a “low-BAC DUI” carries lighter penalties. The consequences are the same as a standard 0.08 percent conviction under Vehicle Code 23536.

For a first offense, you face:

• Up to six months in the San Bernardino County jail
• Fines and assessments that can total thousands of dollars
• A mandatory DUI education program (3, 6, or 9 months)
• A driver’s license suspension
• The requirement to install an Ignition Interlock Device (IID) for a specified term if ordered by the court under 2026 guidelines

If the DUI involved an accident or injury, the charges can quickly escalate to a felony under Vehicle Code 23153. The state will use the “combined influence” or “drug impairment” theory to argue that you were a danger to the public, even without a high alcohol reading. For certain felony cases, AB 321 provides a procedural path to argue that a “wobbler” offense should be handled as a misdemeanor, which we utilize to protect our clients’ records.

Why You Need an Aggressive Defense Team

The prosecution has a team of “experts” and unlimited resources to prove you were impaired. You need a team that is more educated and more prepared than they are. We have spent decades mastering the science of DUI defense. We do not just look at the police report; we also consider the raw laboratory data, the equipment maintenance records, and the arresting officer’s training history.

A DUI arrest is an accusation, not a conviction. Whether the police are claiming you were impaired by alcohol, prescription drugs, or a combination of substances, we know how to fight back. We investigate the errors the police made during your stop in Redlands. We find the inconsistencies in their testimony. We protect your future by attacking their evidence from every angle.

Start Your Defense with a Free Consultation

Your life does not have to stop because of a DUI arrest. You have exactly 10 days from your arrest to request a DMV hearing to protect your license. If you wait, you automatically lose that right. 

We are ready to step in and handle both the DMV and the criminal court case for you. Our reputation is built on winning cases and providing our clients with a defense that most other lawyers cannot match. We offer free consultations to anyone facing DUI charges in the Redlands area. 

Contact Patrick Silva, Attorneys at Law, today at 909-500-4819. Let us show you how we win.