A driving under the influence (DUI) or driving while intoxicated (DWI) can be a difficult thing to face. If you are facing charges and a trial you need a good attorney who can represent you with a valid set of defenses.
If you have been charged, the prosecution needs to prove that you drove a vehicle or had control of a vehicle and that you were “under the influence” of alcohol or other drugs at the time.1 Basically, they must prove that your ability to drive safely was impaired by alcohol, a drug, or a combination of both.2 Therefore, a defense to a DUI/DWI case can be anything that proves either of these two elements wrong.3 Of course, defenses are highly specific to your case and will depend on what happened at your arrest. Therefore, it is best to consult a DUI attorney about your case to see how to proceed.
Driving / Control Defenses
If you were charged when you were not driving, or if there is a question about whether or not you were in control of a vehicle, this could be a valid defense. You may also bring up the more rare defense that you were not the driver or that you were unaware that you were driving.4 As mentioned in sections below, these defenses do not come up often and their success depends largely on your personal situation.
There are always constitutional defenses related to your arrest. If the police officer who pulled you over did not respect your constitutional rights or did not follow the proper legal procedures, the evidence against you may be inadmissible or kept out of the court.5 Therefore, there are several defenses available concerning your arrest if something was improperly done, including breathalyzer and other field sobriety tests.
In order to make an arrest without a warrant, a police officer needs probably cause to think that a crime has been committed.6 A main defense in this arena is any challenge to the police officer’s testimony. The arresting officer will probably testify in court about how you were driving or how you performed on the field sobriety test to establish probable cause.7
Once you are arrested or in any sort of custodial interrogation by a police officer, the officer must read you Miranda warnings so you are apprised of your Fifth Amendment rights to remain silent and to obtain counsel.8 If these warnings were not given to you when you were taken into custody, any statements you make to the police could be excluded at trial.9
No Knowledge of Impairment or Driving
Whether or not knowledge is a factor depends largely on the circumstances of your arrest, which statute you are accused of violating, and any facts surrounding your situation. In general, a DUI/DWI is a strict liability offense in Arizona, and thus intent or knowledge is not a factor to consider. Therefore, the “unknowing” consumption of alcohol has not been held as a valid defense, especially to an aggravated DUI charge.10 This may be different from an involuntary intoxication charge. In one unpublished case, a man was charged with an aggravated DUI and argued that he was unaware that Tilt (a malt liquor containing approximately 6-8% alcohol) had any alcohol in it.11
Conversely, in another Arizona case a man who was caught driving on a suspended license while taking a chemical marketed as a steroid had his aggravated DUI charge reversed.12 When the officer pulled him over because of his strange driving habits they did some tests and saw that he was driving impaired; that is, he was under the influence of a central nervous system depressant.13 The driver knowingly ingested a substance that was not banned, but when the substance came in contact with water, it transformed into a prohibited substance.14 Boyd successfully asserted the defense that Arizona statutes defining the type of drugs and behaviors that were prohibited violated his due process because in his case they failed to give him notice that his actions were illegal.15
Each specific defense depends on your case. In another case, the Arizona Court of Appeals rejected the defense that an Arizona statute’s failure to mention a depressant found in the driver’s system made the statute vague.16 The driver had been driving erratically while her children who were under age 15 were in the car.17 She had taken Ambien and Celexa, two central nervous system depressants, and claimed that her driving was not voluntary because the combined drugs effectively made her “sleep drive.”18 The court rejected this defense.19 The court made a point to note that Arizona statutes do not have to specifically list drugs such as Ambien in a list of prohibited drugs to provide notice.20
If you have been charged with a DUI/DWI and believe one or more of these defenses applies to you, it is best to consult an experienced attorney who can help you navigate what to assert and what not to.
 Kathleen Michon, DUI and DWI Defenses, nolo.com, http://www.nolo.com/legal-encyclopedia/dui-dwi-defenses-32254.html (last visited Oct. 28, 2014).
4 Defenses to Drunk Driving, dui.findlaw.com, http://dui.findlaw.com/dui-cases/defenses-to-drunk-driving.html (last visited Oct. 28, 2014).
5 Kathleen Michon, supra note 1.
6 Search and Seizure, legal-dictionary.thefreedictionary.com, http://legal-dictionary.thefreedictionary.com/Probable+Cause+and+Reasonable+Suspicion (last visited Oct. 28, 2014).
7 Kathleen Michon, supra note 1.
8 Search and Seizure, supra note 6.
10 State v. Blanco, No. 2 CA-CR 2010-0179, 2010 WL 4924959, at 2 (Ariz. Ct. App. Dec. 2, 2010).
11 Id. at 1.
12 State v. Boyd, 201 Ariz. 27, 29, 31 P.3d 140, 142 (Ct. App. 2001).
14 Id. at 143.
15 Id. at 142
16 State v. George, 233 Ariz. 400, 313 P.3d 543 (Ct. App. 2013).
17 Id. at 401
18 Id. at 402.
20 Id. at 403.