who prosecutes dui cases?

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. However, specific DUI laws and penalties vary by 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.

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 (.05% or more in Utah). (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 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.

Impairment DUI laws typically apply to legal and illegal substances alike. So, you can be charged even if you have a doctor's prescription or the drug you took is legal in your state.

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.

Some state laws prohibit driving under the influence anywhere in the state. These laws make it easy for 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.

Prosecutors may be called county attorneys, city attorneys, district attorneys or states' attorneys. Some jurisdictions may even have experienced police officers act as prosecutors in drunk-driving cases.

In order to prove that a defendant is guilty of driving under the influence, the prosecution must be able to prove that the defendant drove a vehicle and that he or she was under the influence of drugs or alcohol at the time of driving or had a BAC of 0.08 percent or higher at the time of driving.

In many cases, the arresting officer will personally observe the defendant driving a vehicle. However, in some cases the officer may not actually see the defendant drive a vehicle and the prosecution must be able to prove driving by some other means. This is often the case in DUI collisions where the officer was not present when the collision occurred. The prosecution may rely on witness statements to prove that the defendant was driving or the defendant’s own admission that he or she was driving the vehicle.

In some cases, there may be no witnesses or admissions. In these cases, the prosecution may try to prove that a defendant was driving by using circumstantial evidence. This can include the position of alleged driver in the vehicle, the lack of other possible drivers or other factors that tend to show the defendant was the driver.

It is important to remember that in California, the prosecution must show more than mere physical control of a vehicle. Courts have found that driving requires volitional movement of a vehicle. This means that defendants who were sleeping or sitting in a vehicle and not actually driving would have a strong defense if charged with DUI.

The prosecution must be able to prove that the defendant was under the influence of alcohol at the time of driving or had a BAC of 0.08 percent or higher at the time of driving if charged with California Vehicle Code Section 23152(b) VC. To do this, the prosecution will rely on the results of the breath or blood test taken after the time of driving. Drivers must be observed prior to testing at all times to ensure they do not consume alcohol or do anything else that may lead to higher BAC results.

The prosecution may have to provide expert testimony regarding retrograde extrapolation to explain how the results of a test taken after the time of driving can accurately show the defendant’s BAC when driving occurred. The defense can also present expert witnesses who may be able to show why the defendant’s BAC at the time of driving was under 0.08 percent and subsequent test results reflected a rising blood alcohol level.