DUI Defenses

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 What Does it Mean to be Charged with a DUI?

Driving under the influence (DUI) is a serious offense that involves a driver operating a motor vehicle while being under the influence of prohibited amounts of alcohol or other substances.

A driver may also face a similar charge known as driving while intoxicated (DWI).

To prove a DUI charge, the prosecution must establish that the person charged was driving the vehicle and was indeed under the influence.

State laws usually determine the specific criteria for a DUI case.

What Are the Affirmative Defenses to a DUI Charge?

When faced with a DUI charge, there are several affirmative defenses that a person may present in court.


This defense is allowed if the driver had to operate the vehicle to prevent a greater evil. The person must prove that the harm caused by the DUI was less serious than the potential harm that could have resulted from not driving.

Suppose a person is at a party and has consumed alcohol, putting them slightly over the legal limit.

Suddenly, they receive a phone call that their spouse has had a medical emergency at home, and an ambulance is unable to reach their remote location quickly enough.

In this scenario, the person may choose to drive under the influence to save their spouse’s life, as the potential harm from not driving (the spouse’s life is in danger) outweighs the harm caused by the DUI.


This occurs when someone forces the person to operate the car while intoxicated through the use of force or threat of force.

Imagine a scenario where a person has been intoxicated at a bar.

As they leave the bar, they are approached by a threatening person with a weapon who demands that the intoxicated person drive them to a specific location.

In this case, the driver may use the defense of duress, as they were forced to drive while intoxicated due to the threat of harm.


A person may claim entrapment if a law enforcement officer encourages the driver to become intoxicated.

Consider a situation where an undercover police officer poses as a friend and pressures someone into consuming alcohol, despite their initial reluctance.

The officer then insists that the person drives them home, even though the person is now intoxicated.

In this instance, the individual may claim entrapment as their defense, as the officer encouraged the driver to become intoxicated and then insisted they drive.

Mistake of Fact

This defense applies when the person genuinely believes they were not intoxicated.

Imagine a person attending a party and consuming what they believe to be non-alcoholic beverages, only to find out later that the drinks contain alcohol.

They then drive home, believing they are sober, but are pulled over and arrested for a DUI. In this case, the driver could use the mistake of fact defense, as they genuinely believed they were not intoxicated when they drove.

Involuntary Intoxication

A person may claim involuntary intoxication if they consumed alcohol unknowingly.

Suppose someone is at a social gathering where drinks are being served. They consume a beverage that they believe is non-alcoholic, but it has been spiked with alcohol by someone else without their knowledge.

They then drive home, unaware that they are intoxicated, and are subsequently charged with a DUI. In this situation, the driver could claim involuntary intoxication as their defense since they unknowingly consumed alcohol.

Common Defenses Employed in DUI Cases

In addition to the affirmative defenses mentioned above, there are other common defenses used in DUI cases:

  1. Improper stop: Defense attorneys often argue that the initial stop by the officer lacked probable cause and was, therefore, invalid.
  2. Accuracy of field sobriety test (FST): The validity of the FST depends on its accurate administration. The horizontal gaze nystagmus (HGN) test, which detects eye movements related to intoxication, is often challenged.
  3. Accuracy of portable breathalyzer test: Defense attorneys may challenge the test based on intervening factors such as indigestion or vomiting and whether the test was properly conducted.
  4. Accuracy of standard breathalyzer test: This test is typically administered after the arrest at the police station.
  5. Chain of custody of blood test: This defense considers whether the blood test was tampered with.
  6. Rising blood alcohol concentration: This defense is related to recent alcohol consumption and whether the blood alcohol level had reached the prohibited level at the time of the arrest.

There are also less common defenses used against DUI charges:

  1. The accused was not the driver.
  2. Improper police action.

In some states, a person can be charged with a DUI even if the vehicle is not in motion, as long as they have physical control and are operating the car.

Defenses Regarding Arrest Procedures in DUI Cases

Law enforcement officers need probable cause to stop a vehicle for a DUI. If there is no valid reason for the traffic stop, any evidence obtained following the arrest may be deemed inadmissible.

In addition to having a valid traffic stop, the officer must also have a reason to believe that the driver violated DUI laws.

This usually happens after the officer observes the driver’s behavior and administers various sobriety tests. If the tests show that the driver’s blood alcohol level was above the legal limit, this is enough for the judge to find probable cause.

The officer must also recite the Miranda rights to the person in custody before questioning begins.

Challenging the Officer’s Testimony in DUI Cases

In most states, there are two types of DUI charges: “impairment” DUI and “per se” DUI.

For impairment DUI cases, an officer can cite the following observations:

  1. Poor FST performance.
  2. The odor of alcohol.
  3. Reckless driving.
  4. Bizarre behavior.
  5. Slurred speech.
  6. Bloodshot eyes.

Defending against the officer’s observations can be challenging, but every case is unique. For example, you could introduce another witness who had a different account of the events leading up to your arrest for the DUI.

However, the prosecution may try to discredit that witness by claiming they are biased, especially if they were a passenger in the car with the driver. You can also provide valid explanations for your appearance and behavior.

If the officer fails to provide necessary information or warnings, it could affect the admissibility of the tests. For example, if you refuse to take a chemical test, your license could be suspended. If the officer fails to inform you of this consequence, the test results may not be admissible in court.

When Should You Contact a Lawyer for Help with a DUI Case?

If you have been arrested or charged with a DUI, options may be available to you for receiving a lesser punishment based on your circumstances. However, this availability depends on the specific state laws and your situation.

If you believe that your rights as a driver have been violated or there was misconduct by the police officers, you may have a defense for your DUI charge.

To explore the available DUI defenses, use LegalMatch today to consult with an experienced and knowledgeable DUI lawyer who can help you navigate the legal process and resolve any issues related to your DUI case.

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