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 DUI and want to fight the charge, you should understand all of 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.
In a DUI case, the prosecution must prove the person being charged (the "defendant"):
Most DUI defenses target one these two components because the prosecution must prove both to get a conviction. The defenses available to a DUI defendant depend—to some extent—on state law. But this article gives an overview of some DUI defenses that are available in most states.
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 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 "operating" or "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.
(Learn more about the possibilities of getting a DUI without actually being caught driving.)
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—certain evidence should be thrown out.
No Probable Cause for Arrest
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. 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 police pull you over without a legitimate reason, a court is likely to say all the evidence subsequently obtained is inadmissible in court.
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 field sobriety tests (FSTs), smelled of alcohol, and had slurred speech. For most judges, that would be enough for probable cause. And in most situations, breathalyzer results showing your blood alcohol concentration (BAC) was over the limit are going to make challenging probable cause an uphill battle.
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. (Find out more about Miranda rights and police questioning.)
All states have two types of DUI charge: one based on actual impairment (an "impairment" DUI) and another based on the amount of drugs or alcohol in the driver's system (a "per se" DUI). For proving an impairment DUI, 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.
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.
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.
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