Arrested? Suffering from a past conviction?

Call us or Click Here to schedule your free, in-person (weekends often available).

If our operators are busy, leave a detailed voice message.

Contact Us Now!

DUI Legal Defenses

Driving under the influence (DUI) cases are usually complicated matters, and for some, fighting a DUI charge can feel insurmountable. However, fighting off a DUI charge is not as hopeless as they seem to be. Regardless of the circumstances and evidence against you, there always several approaches that you can try to fight off a DUI charge.

Pleading guilty to a DUI is something that a lot of people do when confronted with the evidence against them. However, by exploring all possible defense strategies available for your case, a skilled attorney can persuade a prosecutor to agree to reduce the charges or even dismiss the charges altogether. That is why it is always advisable to consult with an experienced DUI defense attorney rather than facing these charges by yourself.

To help give you a better understanding of how to fight your DUI charge, our defense attorneys will discuss some of the top legal defenses against DUIs in the following article.

Contesting Breath Tests

Breath testing is one, if not the most common method employed by California police officers when determining a driver’s blood alcohol concentration or “BAC.” The device used to conduct the breath test, known as “breathalyzers”, are not perfect and can be subject to a variety of errors due to malfunctions, mishandling, driver’s condition when the test was taken, and other environmental conditions.

Keep in mind that a breath test does not measure the amount of alcohol in your blood. Rather, it measures the amount of alcohol absorbed in the deep lungs tissue, that is eventually released through your breath. The device then converts that value and approximates the equivalent amount that may be found in your blood. There are many possible reasons for the “mouth alcohol” to be high but that does not necessarily mean that it came from an alcoholic beverage. This is the reason why some breath tests show erroneously high values. Understanding how breath tests work and the protocols involved can be the foundation for a successful DUI defense strategy. Residual mouth alcohol will be better explained in the remainder of this article.

Contesting Blood Tests

Blood testing is the other common form of testing used to measure BAC. Certain chemical reactions can lead to a high BAC in the blood. For example: blood fermentation, contamination of the blood sample, improper handling or storing of the blood sample, etc.

Your attorney can file a “blood split motion” to learn more about how your blood sample was handled and stored, and the testing conducted to your blood. Understanding how blood tests work and the protocols involved can be the foundation for a successful DUI defense strategy.

Residual Mouth Alcohol

Residual “mouth alcohol” is another important DUI defense. As mentioned earlier, breath tests measure the amount of alcohol absorbed by the deep lung tissue that is eventually released through your breath. This can only be found in the deepest part of the lungs and that is called "alveolar air." However, breathalyzers do not always read the deep lung air and can sometimes capture alcohol readings that are not from the alveolar air. This can sometimes come from small pieces of food caught in the mouth that is soaked in alcohol, or from burping, mouthwash, chewing gum, acid reflux, etc.

Due to the other possible sources of alcohol in the mouth, the breath test can sometimes result in erroneously high BAC readings. However, keep in mind that this defense is only applicable if you took a breath test and not a blood test.

Rising Blood Alcohol

Rising blood alcohol is a defense that can be applied with a breath test or a blood test. Rising blood alcohol simply means that a test was taken when your body was still in the process of absorbing alcohol that was consumed. It takes time for the body to absorb alcohol and this can vary between 50 minutes to 3 hours, depending on each person.

For example, you just finished a drink and got in your car immediately after to take a short drive. While you were driving, you were arrested and took either a breath or blood test. When the test was conducted, your body was still in the process of absorbing the alcohol so the alcohol in your blood was still rising. When this happens, the test result can show a high BAC reading. This does not necessarily mean that you were drunk when you got in your vehicle, but rather, the test was taken during a time when your body was still in the process of absorbing the alcohol, hence the high BAC reading.

For DUIs, what matters is your BAC when you drove your vehicle and not when the test was taken. This is an important distinction that can be useful in coming up with an effective defense strategy in DUI cases.

Medical Condition as a DUI Defense

Some illnesses are scientifically recognized to create "mouth alcohol" conditions. For example: heartburn, acid reflux, GERD, hiatal hernia, auto-brewery syndrome, ketosis, to name a few.

If you have any of these conditions when the breath test was taken, the gases and other chemicals in your stomach that travel to your mouth can be read by the testing device as BAC.


Ketosis is another condition that can create "mouth alcohol." Ketosis happens when the body is deprived of carbohydrates and then consume stored fat for energy. This metabolic process produces ketones. Ketones, when eliminated from the body, produce isopropyl alcohol. This produced isopropyl alcohol can be mistaken by breath test devices as ethyl alcohol. Ethyl alcohol is the type of alcohol found in alcoholic beverages. Ketosis can happen when a person has diabetes or consumes a low-carbohydrate and high-protein diet.

Misapplication or Violation of Title 17 of the California Code of Regulations

Title 17 of the California Code of Regulations lays down the rules for the collection, storage, and analysis of chemical testing done for DUI cases.

The rules are specific, and any violation can lead to errors that can affect the integrity of your BAC results. It requires calibration of equipment, sanitation of equipment, training of technicians who conduct the testing, among other requirements.

If the rules are not followed, your chemical test can be questioned or possibly excluded from evidence.

Lack of Probable Cause

Before a police officer can stop your vehicle, conduct a DUI investigation, and arrest you for suspicion of being under the influence, they must have “probable cause.”

Probable cause means that an arresting office has reason to be suspicious or believe that you were engaging in an illegal activity.[1]

If the arresting officers had no probable cause, any evidence obtained from their DUI investigation can be suppressed. When a judge suppresses evidence, it means that the judge will make an order preventing the prosecution from using suppressed evidence to prove their case against you. If your attorney can successfully prove a lack of probable cause, the charges against you can be reduced, and sometimes even dismissed.

Miranda Rights

In the context of DUI arrests, it is a misconception that Miranda rights have to be read upon arrest. Miranda rights are only necessary when two things happen:

  • You have been arrested
  • After being arrested, you are placed under custodial investigation

When both of these things happen, police are now required to read you your Miranda rights.

Custodial investigation means that after being arrested, police officers ask you questions that are designed to elicit an incriminating response.

Physical Observations of Possible Signs of a DUI

Officers are trained to look for possible signs of intoxication. But sometimes, these signs are merely innocent attributes that could have been caused by different reasons other than drunkenness. Some signs that police look for include red watery eyes, slurred speech, unsteady balance, odor of alcohol, etc.

Even if a person has these physical signs, it does not always necessarily mean that a person is DUI. Sometimes, these signs are merely symptoms of diseases, fatigue, illness, allergies, etc.

Understanding these signs and proving that there is a logical and innocent explanation for these signs can greatly help with your case.

Field Sobriety Tests

These are tests conducted by police officers to determine and identify indicators of drunkenness. Similar to physical observations, field sobriety tests or FSTs are not always accurate. FSTs have to be administered and scored precisely for the results to be considered trustworthy.

Sometimes, environmental factors can affect the results of an FST. Some of these factors include insufficient lighting, poor weather conditions, officer intimidation, uneven surfaces, etc.

Your attorney will question the results of the FST so the prosecutor cannot present them as reliable evidence for a DUI case.

Poor Driving

Poor driving skills are not equivalent to driving under the influence. Officers will stop a vehicle for weaving, speeding, and other signs of erratic driving and use that as probable cause for a DUI arrest. However, these behaviors can sometimes simply be caused by lack of attention to the road, distraction, nervousness, etc. Sometimes, a person is simply just a bad driver exhibiting the driving of an inebriated person.

Non-Compliant DUI Sobriety Checkpoints

There are strict legal requirements[2] for there to be a valid DUI Checkpoint. 8 rules must be complied with before a DUI checkpoint can be considered valid and constitutional. In particular:

  1. Role of supervisory personnel - Supervisory law enforcement personnel are the ones to decide on the establishment of a DUI checkpoint, the selection of a site, and the procedures for its operation (not the field officers).
  2. Restriction on discretion of field offices- Field officers are not allowed to exercise discretion in choosing which motorists to detain, it must be based upon a mathematical selection formula (i.e., all drivers, or every second driver, or third, fifth, etc. driver).
  3. Safety – DUI checkpoints must be located in areas where a high degree of safety can be assured.
  4. Reasonable location – Checkpoint locations must reasonably suit the goals of safety and the goal of effectively deterring drunk driving and locating drunk drivers.
  5. Time and duration – The time and duration of DUI checkpoints must be based on the sound judgment of the law enforcement supervisory personnel.
  6. Indicia of official nature of roadblock – DUI checkpoints should be established with high visibility, including warning signs, flashing lights, flares, police vehicles, and the presence of uniformed officers.
  7. Length and nature of detention – Each motorist who is stopped should be detained only long enough for the officer to question the driver briefly and to look for signs of intoxication, such as alcohol on the breath, slurred speech, and glassy or bloodshot eyes.
  8. Advance publicity – The public must be given advance notice that sobriety checkpoints are planned, usually by announcement through media (i.e. law-enforcement website, local news stations, local newspapers, advertising, etc.).

Without following these 8 rules, a DUI checkpoint will be deemed unconstitutional and your attorney can effectively challenge your DUI charge.

Error Rates in Chemical Testing

There are recognized inherent error rates for chemical testing. A California DUI chemical testing has a +/- error rate of between 0.005% and 0.02%. This means that BAC results that are between 0.08% and 0.10% can be challenged. This is important to take note of because a BAC that is 0.08% and above is considered above the legal limit.

Radiofrequency Interference

Radiofrequency interference can cause errors with the BAC results because the devices used for testing are susceptible to electromagnetic interference.

Electromagnetic interference can come from various electronic components such as cellphones, microwaves, patrol cars, automatic doors in crime labs, etc.

Lack of Mental Impairment

California law distinguishes between mental impairment and physical impairment. Those observed by officers during a DUI investigation are usually physical impairments. However, according to experts, impairment caused by drugs or alcohol usually manifests first as a mental impairment. Without mental impairment, your attorney has an opportunity to challenge the allegations against you.

BAC Not Representative of Actual Impairment

The level of impairment as opposed to a high BAC can be a sign that there is some inaccuracy to the BAC test results. This is especially visible in the case where

  • You exhibited no impairment, OR
  • You exhibited very slight impairment but had a suspiciously high BAC result

These are sometimes referred to as "Disconnect" DUI cases. Sometimes the evidence, such as the BAC test, results do not logically add up to the other evidence presented in the case. In such a case, your attorney will have an opportunity to challenge the accuracy of the BAC results.

“Driving” in DUI

Although a person could have been under the influence, that person must have been actually driving a vehicle to be charged with a DUI. The police cannot charge you with a DUI if you were merely sleeping in your vehicle that was parked. One of the important elements for the prosecution to prove a DUI is that the defendant must have been driving a vehicle.

BAC Results vs. DUI

As mentioned earlier, there are a lot of ways that a BAC test results can be affected to make it inaccurate. Despite a test result showing BAC, it does not necessarily mean that a person was driving under the influence. Sometimes these errors can come from illness, environmental factors, error in testing, etc.

Due to these factors affecting DUI test results, even if the results show that a person has a BAC above the legal limit, it does not necessarily mean that a person what driving under the influence.

Police Misconduct

The presence of police misconduct can sometimes get a DUI charge dismissed even if all the evidence proves that a person was indeed driving under the influence.

Depending on the circumstances, sometimes police misconduct can severely affect the case the prosecutor’s case against you. A prosecutor may choose to reduce or even dismiss the charges against you if it can be shown and proved that police misconduct was indeed present in your case.

DUIs happen. Losing your license and jail don’t have to.

A DUI charge is a difficult thing to manage and navigate on your own. You will want to consult and secure the services of an experienced DUI defense attorney to assist you in navigating the legal complexities of these charges. You will want to avoid a conviction at all costs because it can have severe effects on your life. Although we are fielding inquiries from a lot of people in similar situations, we will do our best to put you in contact with an experienced lawyer from our firm.

If you need assistance with a DUI charge, do not hesitate to contact us at (626) 827-7222 to schedule your consultation with one of our experienced DUI attorneys at no cost.

[1] Terry v. Ohio, 392 U.S. 1, 20 (1968)

[2] Ingersoll v. Palmer 43 Cal.3d 1321 (1987).

Get in Touch with Second Chances Law Group

Schedule Your Free Appointment with Our Award-Winning Court Attorneys
Freedom at your Fingertips
    • Please enter your name.
    • This isn't a valid phone number.
    • Please enter your email address.
      This isn't a valid email address.
    • Please make a selection.
    • Please enter a message.
  • Must be checked