DUI Defenses: How to Fight a Drunk Driving Charge

Learn about the most common ways to fight a DUI or DWI charge.

By , Attorney · Northwestern University School of Law

The penalties for a DUI (driving under the influence) (also called "DWI" (driving while intoxicated)) offense can be serious. If you've been arrested for a DUI and want to fight the charge, you should talk to a DUI lawyer about the available defenses. With a viable defense, you might be able to persuade the prosecution to drop or reduce the charges, prevent the suspension of your driver's license, or win an acquittal at trial.

What Does the Prosecution Need to Prove for a DUI Conviction?

In a DUI case, the prosecution must prove the person being charged (the "defendant"):

  • drove a vehicle, and
  • was "under the influence"—meaning the person was either impaired or had a prohibited amount of drugs or alcohol in his or her body.

Many DUI defenses target one of these two components (also called "elements") because the prosecution must prove both to get a conviction. The defenses available to a DUI defendant depend, to some extent, on state DUI laws. But this article gives an overview of some DUI defenses that are available in most states.

DUI Defenses Related to the "Driving" Element

In some states, you can't be convicted of a DUI unless you were actually driving a vehicle. So, if you were asleep in a parked vehicle in one of these states when police arrived, you probably have a good defense.

But most states don't require proof of actual driving for a DUI conviction. All the prosecution needs to prove is that you were in "actual physical control" of a vehicle while intoxicated. In other words, you can be found guilty even if you weren't caught behind the wheel with the car in motion.

However, whether a driver was in "actual physical control" of a vehicle is a fact-specific question. If the facts show the arrested person was unlikely to actually put the vehicle in motion, there's a good chance the DUI charge won't stick.

For example, if a drunk person was asleep inside a vehicle but didn't have the keys, it might be hard for the prosecution to convince a jury that the person was in actual physical control of the vehicle.

DUI Defenses Related to Driver Intoxication or Impairment

Evidence of driver intoxication comes in various forms. However, in many cases, there are chemical test results showing how much alcohol and drugs the driver had in his or her system. It's also common for the police officer who made the arrest to testify at trial regarding observation of the driver's impairment.

Challenging the Accuracy of Alcohol and Drug Test Results

Because it's illegal to drive with a blood alcohol concentration (BAC) of .08% or more (.05% or more in Utah)—called a "per se DUI"—chemical test results alone can prove the intoxication component a DUI charge.

When challenging alcohol- or drug-test results, you're typically either saying the results are unreliable because of some flaw in the testing procedure or represent an inaccurate measurement of the amount of drugs or alcohol at the actual time of driving.

Experienced DUI attorneys know exactly what to look for when assessing a case for these types of defenses. Defenses related to chemical test results might also require the testimony of an expert witness who can explain why the results of the state's tests are unreliable.

Challenging the Officer's Testimony About Signs of Intoxication

For proving a DUI based on actual impairment (as opposed to the amount of drugs or alcohol in the driver's system), the officer's observations can be an important part of the prosecution's case. An officer's observations of impairment might include:

To beat a DUI charge, the defense might need to challenge the significance of an officer's observations. It just depends on the circumstances, but it can be difficult to convince jurors that the officer's conclusions about the driver's intoxication were wrong.

Introduce Witnesses Who Saw Things Differently

One way to challenge an officer's observations is to bring in witnesses who were present when you were arrested and saw things differently than the officer. Unfortunately, in many cases, there aren't any witnesses. Or, if your witness was a passenger in your car, the prosecution might argue that your witness is biased.

Offer Valid Explanations for Your Appearance and Behavior

For some officer observations, you might be able to provide an explanation—other than intoxication—for what happened. For example, fatigue and physical disabilities can lead to poor FST performance. And bloodshot eyes can be caused by allergies and other irritants.

When Field Sobriety Tests are Unreliable

In challenging the accuracy of FST results, attorney look for ways in which the officer might have failed to follow protocol in administering the tests. For example, some of the tests must be performed on a flat surface. So, if the driver was made to perform FST on a sloped road shoulder, the defense can use this fact to cast doubt on the officer's ultimate conclusions.

DUI Defenses Related to Illegal Traffic Stops and Unlawful Arrests

When police don't use proper arrest procedures, it can sometimes provide you with a good defense to a DUI charge. Defenses related to arrest procedures typically involve arguing that—because police didn't follow the law when stopping or arresting you—the judge should throw certain evidence out.

Generally, police need probable cause to stop your vehicle, and if they're going to arrest you for a DUI, they need probable cause for that too.

Illegal Traffic Stops in DUI Cases

For the traffic stop, police have probable cause if there's reason to believe the driver or someone else in the vehicle has broken the law. (DUI checkpoints and roadblocks are, however, an exception to the probable cause rule.) Basically, any traffic violation will suffice. But if the police pull you over without a legitimate reason, a judge is likely to say all the evidence subsequently obtained is inadmissible in court.

No Probable Cause for DUI Arrest

A valid traffic stop doesn't necessarily make a DUI arrest proper—the officer must also have reason to believe the motorist was in violation of the state's DUI laws. Probable cause for a DUI arrest usually comes from the officer's observations and sometimes breath-test results.

Both forms of evidence can be tricky to challenge. An officer might say you performed poorly on FSTs, smelled of alcohol, and had slurred speech. For most judges, that would be enough evidence for probable cause. And in most situations, breathalyzer results showing your BAC was over the limit are going to make challenging probable cause an uphill battle.

Failure to Give Miranda Warnings in DUI Cases

Occasionally, Miranda warnings come into play in DUI cases. Police are generally required to give Miranda warnings prior to questioning a suspect who's in police custody. So, if a DUI suspect who's in police custody and hasn't been given Miranda warnings makes an incriminating statement in response to police questioning, the statement probably can't be used in court against the suspect.

Talking to a DUI Attorney

This article goes over some basic information about DUI defenses, but there's no substitute for the help of a knowledgeable attorney. If you've been arrested for driving under the influence, you should get in touch with a qualified attorney as soon as possible.

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