Two DUI Charges: Driving Under the Influence & Driving with a BAC Greater Than .08

If you’ve been charged with a DUI, chances are great that you've actually been charged with two offenses—driving under the influence and driving while having a blood alcohol content (BAC) of .08 or more. These are separate offenses and if you go to trial you will have to defend both of them. However, at trial or if you plead guilty, one of these charges will likely be dismissed (but not in all states). Let's take a detailed look at each charge.

Driving Under the Influence

Most states' laws forbid driving a vehicle under the influence of an alcoholic beverage, under the influence of a drug, or under the combined influence of an alcoholic beverage and any drug. The typical elements of this offense that must be proven in order to convict you are:

  • you drove (operated) a vehicle (which in some states includes boats)—that is, you were in control of the vehicle (in some states, even if you were asleep at the wheel at the side of the road when the officer found you), and
  • while you operated the vehicle your physical or mental abilities were impaired to at least some degree.

As for the operation requirement, it usually is satisfied by a police officer or a witness who saw you driving. On occasion, however, especially after an accident, you may be out of the car when the officer arrives and the operation element is proven either because you admit you were driving or the officer deduces from all the evidence that you were driving.

In some states, you could be charged with a DUI even you're found in the car with the engine turned off and the keys in your pocket. However, in other states where a DUI strictly requires you to be in control of a car while it is moving, you most likely would not be charged with a DUI. Go to to see what your state's laws say about the operation requirement.

In some but not all states, you must have been operating the vehicle on a public roadway. In other states it makes no difference where you were operating the vehicle even if it was on your own property. And the vehicle need not be a car. For instance, it is possible to be charged with DUI for operating a golf cart on a private golf course.

As for the "under the influence" requirement, the states differ on how this element is defined. For example, in California, the prosecution must prove that you were impaired to a degree that you couldn't drive with the same caution or care as a sober person under the circumstances. In Colorado, the prosecutor needs to prove only that you were impaired to the "slightest degree." And other states frequently use an "impaired to an appreciable degree" standard or some subtle variation of that.

The fact is, you won't really know the exact meaning of these words in your state's laws unless you read the instructions that the judge will give the jury if you go to trial. Fortunately, these jury instructions likely are available in a local law library, or perhaps on your court's website. As a last resort, Google "(your state) criminal jury instructions online" and see what comes up. 

Driving Under the Influence of Marijuana and Other Drugs

The vast majority of DUI prosecutions involve solely alcohol. However, a significant percentage of prosecutions are for operating a vehicle under the influence of marijuana, other drugs, and or a combination of these or other drugs and alcohol. The fact that marijuana or other drugs may be implicated in your case is usually established through a laboratory analysis of a blood or urine sample (in addition to the arresting officer's opinion). Drugs found in the vehicle or the odor of marijuana present at the initial stop may also provide evidence against you.

While the definition of driving under the influence of drugs is usually the same as for alcohol (your ability to drive is impaired in some way), there currently is no offense similar to driving with a BAC of .08 or greater. That's because the science has not yet produced BAC levels at which various drugs can reliably be presumed to cause driving under the influence. There are lots of studies about the effect of alcohol on driving that underscore expert testimony offered by the prosecution in the typical case but few convincing studies on the effects of marijuana on driving. If the prosecutor is relying on a blood or urine test for the presence of THC, the state's expert witness (the toxicologist) may not be able to establish a causal link between the THC and impairment while driving. Of course, if a jury hears that you were smoking marijuana at the time you were stopped, or that other objective evidence of impairment is present—such as showing impairment on the field sobriety tests, you may well face a guilty verdict.

If you are taking a prescription drug that warns you against operating heavy machinery, definitely find a designated driver. Even though a prescription drug maybe appropriately prescribed, socially accepted, and medically helpful, you may be prosecuted for DUI if that drug has an effect on your mental or physical capacities while you are driving. As more and more states adopt medical marijuana laws, it's important to remember that the DUI rules will apply to the medical marijuana user the same as anyone else. Simply put, whether the use of a drug is legal or illegal, its use can result in a DUI if it affects your ability to drive.

 DUI Per Se

The second offense you may be charged with is driving with more than .08 BAC. Laws and lawyers frequently refer to this offense as DUI "per se." Almost all states prohibit the operation of a vehicle on a public road if you have a blood alcohol content of more than .08. The offense occurs regardless of whether the alcohol had (or could have) any effect on your driving. Just driving with that particular blood condition can result in the same repercussions as described for driving under the influence. Not only is this a stand-alone offense, but having that amount of alcohol in your blood can be used to convince a jury that you were also under the influence.

If you are not of legal drinking age, your state may prohibit you from having any alcohol in your system at all.  This means that you can be charged with a DUI per se, even if you drive with even a trivial amount of alcohol in your blood.

Get Help From an Attorney

If you’ve been charged with a DUI and you want to fight the charge in court, seek help from an experienced attorney who is familiar with the laws and procedures in the county where you were charged. 

Excerpted and adapted from Beat Your Ticket: Go to Court & Win, by David W. Brown (Nolo).

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