How a DUI Is Proven

Learn about the elements of a DUI and the evidence used to prove them

By Canaan Suitt, J.D. | Last updated on June 30, 2023 Featuring practical insights from contributing attorney Daniel J. Larin

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Approximately 31 percent of all crash fatalities in the United States involve alcohol-impaired driving, according to the National Highway Traffic Safety Administration (NHTSA). Driving under the influence of alcohol or drugs puts yourself, as well as passengers, other drivers, and pedestrians at great risk.

Because of this, every state imposes severe penalties for driving under the influence. Depending on where you live, the crime of drunk driving might be called Driving Under the Influence (DUI), Driving While Intoxicated (DWI), or Operating Under the Influence (OUI).

Regardless of the label, a DUI conviction will have serious consequences for the rest of your life.

If you’ve been charged with a DUI, you might be wondering:

  • What are the elements of a DUI offense?
  • What evidence do prosecutors use to prove DUI charges?
  • What are the defenses to a DUI?

This article will cover these questions and point to legal help. If you’ve been charged with a DUI, it’s essential to speak with a qualified defense attorney who can “help you navigate the legal system” and give your defense its “best shot,” says Michigan DUI defense attorney Daniel J. Larin.

What is a DUI Charge?

The legal definition of a DUI offense varies from state to state. However, two general elements of a DUI offense hold across the board. In order to convict someone of a DUI, a state prosecutor must prove beyond a reasonable doubt that the defendant was:

  • Operating or driving a vehicle
  • While under the influence

Let’s look at these elements in more depth.

Requirement 1: Operating or Driving

Driving a car while drunk is the most obvious example of a DUI. But you don’t necessarily have to be driving to be convicted of a DUI.

That’s because some state laws refer to “operating” or “being in actual physical control” of a vehicle instead of “driving” a vehicle. Operating or being in control of a vehicle certainly includes driving but might also encompass:

  • Sitting in a parked car with keys in the ignition or with the engine on
  • Being parked on the roadside or in a public parking lot
  • Sleeping behind the wheel while intoxicated

Courts will look at a few factors to determine if someone was operating or in physical control of a vehicle while intoxicated:

  • Where was the driver? For example, were they inside or outside the car? Were they asleep behind the wheel or in the car’s back seat?
  • Where was the car? Was the person driving the car on a public road, or was the car parked? If the car was parked, was it in a parking lot, on the roadside, or in the middle of the road?
  • Where were the keys? Did the driver have the keys in the ignition, or were the keys stored in the dash or kept outside the car?
  • Could the car be driven? If the car was inoperable for some reason, that could help the accused DUI offender’s case.

Another potential issue with the driving element is what counts as a “vehicle.” A car clearly counts, but many state laws cover golf carts, boats, snowmobiles, motorcycles, and mopeds as well.

When it comes to drinking and driving, people often think they can get the charges negotiated down without an attorney. What they don’t realize is that there’s often something in the case [they’re not aware of, but that an attorney] would know about, and that becomes a defense that can lower the charge below a DUI. It’s always imperative to at least have an attorney look at your case and see if there is something that can be done… An attorney can walk you through the system and you’ll know you’ve given it your best shot.

Daniel J. Larin

Requirement 2: Under the Influence

The second element of a DUI offense is “under the influence.” Often, this means being under the influence of alcohol. However, state DUI laws target other substances as well, including legal prescriptions and controlled drugs.

“You can actually get a drunk driving charge and conviction if you’ve taken prescription medication that impairs your ability to drive–for example, a muscle relaxant or a couple of swigs of NyQuil before getting in the car,” says Larin.

“While your BAC wouldn’t be high at all from taking these medications, you could still be pulled over for noticeably impaired driving. With the proper evidence, prosecutors could convict you for something like that.”

DUI Arrests and Investigation

States have implied consent laws that say, if you drive in the state, you have consented to testing if stopped by a police officer who has a reasonable suspicion you’re intoxicated.

So, if a police officer sees a car speeding or swerving erratically, they’ll pull the driver over. Things that can give the officer a reasonable suspicion of intoxication include:

  • The driver’s slurred speech or bloodshot eyes
  • The odor of alcohol or drugs
  • The presence of alcohol or drug paraphernalia

The officer can then request that the driver take a field sobriety test, or a breath test to measure blood alcohol content. You can refuse to take a test, but refusal often carries penalties such as driver’s license suspension and fines.

Types of Evidence in a DUI Case

There are two general ways for prosecutors to prove that someone was under the influence: DUI per se and DUI impairment.

The first way for a prosecutor to prove that a driver was under the influence is by showing that they had a blood alcohol concentration (BAC) level above the legal limit.

In most states, the legal limit for drivers over 21 years old is 0.08 percent. For drivers with a commercial driver’s license, the limit is usually 0.04 percent. For drivers under the legal drinking age of 21, the limit is much lower—often 0.02 percent. It’s important to know your state’s legal limits before refusing a test.

Common tests to measure blood alcohol levels include:

  • Breathalyzer test
  • Chemical tests: blood test or urine test

Evidence in DUI Impairment

The other way a prosecutor can prove a DUI is by showing that the driver was actually impaired by alcohol or another substance. With DUI impairment, a driver could be under the legal limit, but they were still driving unsafely due to alcohol or drugs.

Impairment DUIs are generally more difficult for prosecutors to prove since they can’t simply point to the legal limit.

The prosecutor must prove impairment beyond a reasonable doubt, using various kinds of evidence, such as:

  • Videos or photos of the arrest
  • The officer’s police report
  • Other witness testimony
  • Other evidence such as alcohol or drugs in the car

DUI Penalties

Penalties for a DUI conviction vary depending on state law and circumstances. In most states, a first-time DUI is a misdemeanor and can result in:

  • Fines
  • Jail time
  • Community service
  • Driver’s license suspension
  • Installation of an ignition interlock device (IID) on your car that requires a breath alcohol test to drive

A DUI can be elevated to a felony given a few factors, including:

  • A BAC well over the legal limit of .08 percent;
  • If you already have a DUI on your record; or
  • If there were aggravating factors, such as property damage or harm to others.

Learn more about the consequences of a DUI.

Potential Defenses to DUI Charges

Common defenses to DUI charges include:

  • Contesting the results of a chemical or breath test due to faulty equipment or improper administration of tests
  • Disputing the evidence that you were impaired by alcohol, such as photo/video footage or witness testimony
  • Arguing that the arresting officer failed to follow the correct procedures

Every DUI case is different, and state DUI laws are complex. Therefore, the best way to formulate a defense strategy is to speak with a criminal defense attorney who has experience in DUI cases.

Find an Experienced DUI Attorney

If you’re facing DUI charges, contact a DUI defense lawyer for legal advice as soon as possible.

“When it comes to drinking and driving, people often think they can get the charges negotiated down without an attorney. What they don’t realize is that there’s often something in the case [they’re not aware of, but that an attorney] would know about, and that becomes a defense that can lower the charge below a DUI,” says Larin.

“It’s always imperative to at least have an attorney look at your case and see if there is something that can be done… An attorney can walk you through the system and you’ll know you’ve given it your best shot,” he adds.

Many DUI lawyers provide free consultations. You can search the Super Lawyers directory for a DUI criminal defense lawyer or law firm in your area.

For more information about this area of law, visit our overview of DUI/DWI law.

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