Some defenses allow a case to be won, even when there is strong evidence of intoxication. “Defenses” must be proven by the person charged and should be distinguished from other DWI defense strategies that are focused on attacking any weakness in the case against you. Many of these defenses are unique to DWI, so only experienced DWI attorneys really know and understand how to use these defenses.

Common Drunk Driving Defenses

1. Improper Detention of your vehicle

This is a most frequent argument used by defense attorneys in DWI cases to attack the officer’s alleged probable cause to make the initial traffic stop. Many more cases get dismissed for this type of attack than any others.

2. Accuracy in administering the Field Sobriety Tests

An arrest can be attacked when it is based on an improperly administered field sobriety test.The Horizontal Gaze Nystagmus (HGN) test, which detects eye movements is frequently challenged, because it is so subjective at best and wholly unreliable if not properly conducted. The other tests can be attacked as unscientific, so they are not as reliable, but a jury can still look at the evidence and decide for themselves how important “or not” they are in determining intoxication.

3. Portable Breathalyzer Test 

Every DWI attorney will challenge the validity of the breathalyzer test used at the scene. These are generally considered so unreliable that usually the State’s attorney will agree to not show them to the jury.

4. Standard Breathalyzer Test

These tests are frequently attacked, because they are so important to the State’s case.

5. Chain of Custody of Blood Test

This defense might attack a blood test and/or whether it was tampered with or otherwise mishandled in the chain of custody. One forensic expert states that the blood test is actually easier to attack successfully than the breathalyzer.

6. Rising Blood Alcohol Concentration 

Sometimes a person’s BAC was below the legal limit while you were driving but actually increased between the time of the traffic stop and the breath test. This is possible when recently consumed alcohol is still being absorbed into the system between driving and the time of the BAC test.

Other, Less Common Defenses

1. Accused was not the Driver- Questions may arise over whether the person charged with the DWI actually was driving at the time. Perhaps the passenger, believing he or she was sober, switched places with the driver but failed a sobriety or breath test.

2. Improper Police Actions – This defense may include evidence and/or testimony that the officer violated the defendant’s civil rights, faked a DUI report or otherwise acted improperly

Affirmative Defenses to DWI Charges

1. Necessity is only available when a person must drive to

prevent a greater evil. The driver must prove that he or she had no other options and that the “greater evil” they wished to avoid was more serious than the potential harm caused by a DUI. For instance, if you MUST drive a bleeding relative to the hospital to prevent them from dying.

2. Duress exists when the intoxicated defendant drives ONLY to avoid serious injury or death. For example, someone forces an intoxicated person to drive by threat of force, such as a gun to their head.

3. Entrapment occurs when an officer demands or tricks someone into driving drunk. The defendant must also be able to prove that he or she would not have acted to drive drunk if not for the alleged entrapment.

4. Mistake of Fact – When a person has an honest belief that he or she is not intoxicated. For example, having a valid reason to believe that the impairing effect of one’s prescription medication has worn off.

5. Involuntary Intoxication – When a person has ingested alcohol without his or her knowledge. For example, if the punch bowl at a party was”spiked” with an otherwise unrecognizable quantity of liquor. This one is particularly difficult because the question is “Why didn’t you pull over when you became impaired?”