When you get arrested for driving under the influence, it’s common for the prosecution to file two different DUI charges against you: one based on the amount of drugs or alcohol in your body (a “per se” DUI) and a second based on your level of impairment. But how can a prosecutor charge you with two offenses for one incident? And what’s the difference between the two charges?
The idea behind filing two charges isn’t to convict or punish a motorist for both. Per se and impairment DUIs require different types of proof. So, prosecutors often file both charges in DUI cases with the hope that one or the other will stick. And even if a driver is convicted of the two separate charges, usually the court can only punish the driver for one of the convictions.
Though all states have two types of standard DUI charge, the specifics of how the charges are defined vary by jurisdiction. This article talks about the basics of proving standard DUI charges, including the differences between per se and impairment DUIs.
(Learn about DUI/DWI law and punishments specific to your state.)
To get a DUI conviction at trial, the prosecution must prove beyond a reasonable doubt that you were:
Depending on what state you live in, the prosecutor might also have to prove you were driving on a public—as opposed to a private—roadway. These two (or three) things that the prosecution needs to prove are called the “elements” of the crime.
The main difference between a per se and an impairment DUI is how the prosecution proves you were “under the influence.” Here’s how it works.
Per se DUIs. With a per se DUI, the prosecutor just needs to show the person was driving with a certain amount of drugs or alcohol in the body—proof that the driver was actually impaired or affected by the substance ingested isn’t necessary.
In every state, a motorist can be convicted of a per se DUI for driving with a blood alcohol concentration (BAC) of .08% or more. (For drivers who are under 21 years old, the limit is typically much lower.) Some states also have per se drug DUIs. In these states, motorists with a certain concentration of drugs in their systems are deemed to be under the influence.
Impairment DUIs. To prove an impairment DUI, on the other hand, a prosecutor must show the driver was actually drunk or stoned. The level of impairment that the prosecution must prove varies by state. Laws in some states say a driver is under the influence if affected in any way by drugs or alcohol. Other states require proof that the alcohol or drugs had an appreciable or substantial effect on the driver.
Some states even have two levels of impairment DUIs that carry different penalties. In New York, for instance, a motorist can be convicted of an offense called a “DWAI” (driving while ability impaired) for driving while impaired “to any extent.” But a motorist who is impaired to a “substantial extent” can be convicted of a DWI (driving while intoxicated)—a more serious offense that comes with greater penalties.
Despite what the name, “driving under the influence,” suggests, in most states, you can be convicted of a DUI even if you weren’t actually driving: The prosecution can prove the “driving” element by showing you were “operating” or in “actual physical control” of a vehicle. In these states, actual driving is sufficient—but not required—to prove a DUI charge.
State laws differ on what it means to be operating or in physical control of a vehicle. But the idea behind these laws is the same: An intoxicated person who can quickly take can control of a vehicle and drive away is as dangerous as someone who’s already driving drunk. In deciding whether someone was operating or in physical control of a car, a judge or jury will typically look to a number of factors. These might include:
Generally, the closer a driver was to being capable of putting the vehicle in motion, the more like the judge or jury is to find actual physical control.
(Find out more about the "driving" element.)
Some state laws prohibit driving under the influence anywhere in the state. These laws make it easy on prosecutors—they just need to show the defendant was somewhere within state borders when the offense occurred. The DUI laws in other states, however, apply only to areas that are open to the public. In these states, prosecutors must prove that the roadway where the defendant was stopped was accessible to the general public. (Read more about drunk driving on private property.)
DUI law varies by state, and the facts of every case are different. If you’ve been arrested for driving under the influence, get in touch with a knowledgeable DUI attorney. A qualified DUI lawyer can tell you how the law applies to the facts of your case and help you understand what you’re up against.