All About Tests for DUI in San Jose

If you’ve been accused of a misdemeanor or a serious felony in the San Jose or Silicon Valley Area, a criminal defense attorney can help. At Summit Defense, our goal is always the complete dismissal of all charges. If this isn’t possible, we often negotiate solutions for our clients that allow them to avoid jail and sometimes even prosecution.


Summit Defense
2570 North 1st Street , Second Floor San Jose, CA 95131

All About Tests for DUI in San Jose

If you’ve been accused of a misdemeanor or a serious felony in the San Jose or Silicon Valley Area, a criminal defense attorney can help. At Summit Defense, our goal is always the complete dismissal of all charges. If this isn’t possible, we often negotiate solutions for our clients that allow them to avoid jail and sometimes even prosecution.


Summit Defense
2570 North 1st Street , Second Floor San Jose, CA 95131
Last Modified: August 10, 2023

All about tests for DUI in San Jose

Driving under the influence (DUI) is a serious offense in San Jose, California. It’s crucial to understand the different tests law enforcement officers employ to identify and prosecute DUI offenses. It is time to explore the legal framework for DUI testing, the types of tests (such as a breath test, urine test, or chemical test), their accuracy, and potential legal defenses.

Keep in mind that this is not necessarily something that you need to go through on your own. At Summit Defense, our San Jose DUI attorneys can provide you with the legal representation you deserve. If you are being investigated for driving under the influence or have already been arrested, remember to reach out to us as soon as possible for a case consultation.

Let our San Jose criminal defense lawyer provide you with the strong defense that you expect and deserve.

The Legal Framework for DUI Testing in San Jose

In California, including San Jose, the legal limit for blood alcohol content (BAC) is 0.08% for drivers over 21, 0.01% for drivers under 21, and 0.04% for commercial drivers. The state implements an implied consent law, which means that you consent to chemical testing by driving a vehicle to determine your BAC. Refusal to submit to such tests (including a preliminary alcohol screening test) can lead to severe penalties, including license suspension and fines.

Field Sobriety Tests (FSTs)

Factors that can effect FST results

Field Sobriety Tests are physical tasks used by officers to assess a driver’s impairment. They are typically administered roadside and include three standardized tests recognized by the National Highway Traffic Safety Administration (NHTSA). These tests are only reliable when administered appropriately, and we can review your case to see if any discrepancies could impact the validity of the results.

Horizontal Gaze Nystagmus (HGN) Test

The HGN test assesses the involuntary jerking of the eye as it gazes side to side. Under the influence, nystagmus is exaggerated and occurs at lesser angles. Officers will look for three indicators of impairment in each eye:

  • Lack of smooth pursuit;
  • Distinct nystagmus at maximum deviation; and
  • The onset of nystagmus prior to 45 degrees.

The premise of this test is that people who are under the influence of alcohol might have a difficult time controlling their eyes. So failure to adequately perform this test could be a sign that someone is under the influence of drugs or alcohol.

Walk-And-Turn (WAT) Test

During the WAT test, the driver is instructed to take a few steps, heel-to-toe, along a straight line, rotate on one foot and return in the same manner. Officers look for eight indicators of impairment, including the inability to balance during instructions, stopping while walking, incorrect number of steps, and more.

One-Leg Stand (OLS) Test

In the OLS test, the driver must stand with one foot about six inches above the ground and count for 30 seconds. Officers look for four indicators of impairment, such as swaying while balancing, hopping to maintain balance, or putting the foot down.

Factors That Can Affect FST Results

Several factors can affect FST results, including the individual’s physical condition, the environment, and the officer’s interpretation of the test. For example, individuals with physical disabilities or injuries, older people, and those with balance or inner ear disorders may have difficulty performing FSTs. Environmental factors like uneven surfaces, poor lighting, and adverse weather conditions can also impact performance. Lastly, FSTs are subjective, and different officers may interpret results differently.

DUI Chemical Tests

DUI chemical tests

Chemical tests are used to measure the concentration of alcohol in a person’s system. These tests typically involve the collection and analysis of breath or blood samples. These devices must be appropriately calibrated for the results to be considered reliable.

Breathalyzer Tests

Breathalyzer tests are standard during DUI stops because they’re quick, non-invasive, and provide immediate results. Breathalyzers analyze a breath sample to determine the amount of alcohol in your bloodstream. It’s based on the concept that there’s a direct ratio between the alcohol concentration in one’s breath and blood.

In San Jose, the legal requirements and procedures for breathalyzer testing include the following:

  • We are maintaining the device in working order.
  • They have a qualified professional to administer the test.
  • It is taking at least two separate breath samples.

Blood Tests

Blood tests are considered more accurate than breath tests. They involve drawing and analyzing a blood sample in a lab to determine the exact blood alcohol content. Properly handling and storing blood samples are essential to prevent contamination or degradation, which could impact the results.

Accuracy and Reliability of DUI Tests

Accuracy and reliability of DUI tests

While FSTs and chemical tests are commonly used to determine impairment, their accuracy and reliability can be questioned. FSTs are inherently subjective and rely on the officer’s interpretation of the suspect’s performance. Furthermore, certain medical conditions or physical disabilities can affect a person’s ability to perform these tasks.

Chemical tests, while more objective, also have their limitations. Breathalyzer tests can be affected by factors like device calibration, the person’s breathing pattern, or the presence of mouth alcohol. Blood tests, although more accurate, require proper collection, storage, and analysis procedures to ensure reliable results.

Legal Consequences of Failing DUI Tests in San Jose

Failing a DUI test in San Jose can lead to serious legal consequences. This includes the suspension of driving privileges, hefty fines, mandatory DUI school, probation, and even jail time. The severity of the penalties depends on the circumstances of the offense and whether it’s a first-time or repeat offense.

If you have a clean criminal record, you might not be subject to the same penalties as someone with a lengthy criminal record or a prior history of DUI convictions. No matter your situation, the legal consequences of failing a DUI test in San Jose can be severe, so be sure to contact us to schedule a case consultation as quickly as possible.

DUI Charges and Penalties in San Jose

DUI charges and penalties

In San Jose, a first-time DUI offense can result in penalties, including up to six months in jail, fines up to $1,000, and a six-month license suspension. Penalties increase with subsequent offenses, and aggravating factors like causing injury or death can lead to felony charges. Remember that you may also be required to attend traffic school, perform community service, and remain on probation even if you avoid jail time.

Potential Defenses Against Test Results

While DUI charges are serious, it’s crucial to remember that they can be defended against. A skilled DUI attorney can challenge many aspects of the charges, from the traffic stop to the administration and accuracy of sobriety tests. Some possible defenses that might be used in a San Jose DUI case include the following:

  1. Challenging the Legality of the Traffic Stop: The Fourth Amendment protects citizens from unreasonable searches and seizures. This includes traffic stops. Law enforcement must have a reasonable suspicion of criminal activity, such as a traffic violation or visible signs of impairment, to legally justify a traffic stop. If your attorney can prove that the officer lacked reasonable suspicion or probable cause, the evidence collected, including test results, may be suppressed, rendering it inadmissible in court.
  2. Questioning Field Sobriety Test Administration and Results: FSTs are subjective and depend on the officer’s interpretation. Many factors can influence the results, such as the individual’s physical condition, the environment in which the tests were performed, and the officer’s training and experience in administering these tests. An experienced attorney can challenge the validity of FST results by pointing out these potential issues.
  3. Challenging the Accuracy and Reliability of Breathalyzer Tests: Breathalyzer tests can provide inaccurate results due to various factors. This could include improper calibration or maintenance of the device, the officer’s lack of training in using the device, or physiological factors such as certain medical conditions that can influence the reading. The breathalyzer test results may be invalidated if any of these factors can be proven.
  4. Questioning the Blood Test Results: Blood tests are generally more accurate than breathalyzer tests, but they’re still susceptible to errors. This can occur if the blood sample is mishandled, stored improperly, or the lab procedures for analyzing the sample are incorrect. The blood test results might be deemed unreliable if these issues are identified.
  5. Rights Violations: If your rights were violated during the traffic stop, arrest, or subsequent testing, these violations can be used in your defense.

Remember, every case is unique, and the success of these defenses will depend on the specific circumstances of your case. An experienced DUI attorney can evaluate your situation and determine the best defense strategy.

Contact Summit Defense for an Initial Consultation With Our DUI Defense Attorney in San Jose

Contact Summit Defense for an initial consultation

Facing a DUI charge can be overwhelming, but you don’t have to navigate it alone. At Summit Defense, our experienced DUI defense attorneys are dedicated to protecting your rights and delivering the best possible outcome. Whether it’s questioning the validity of field sobriety tests, challenging the accuracy of breath or blood tests, or scrutinizing the procedures followed during your arrest, we’ll meticulously examine every detail of your case.

Don’t let a DUI charge disrupt your life. Contact Summit Defense today for a free consultation with our DUI defense attorney in San Jose.

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With over 120 years of cumulative and exclusive Criminal Defense experience, our reputation for aggressive and results oriented performance, whether in State court or Federal Court, has been documented by several Bay Area news channels and vetted by hundreds of satisfied clients. Our success and industry recognition is the result of our EXCLUSIVE FOCUS on criminal defense; we don’t accept personal injury or family law cases. This single-minded focus allows us to keep pace with the ever-changing landscape of legal doctrine and provide you with the best results possible.
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Timothy C.
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Ginger W.
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Tony F.
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Connie L.
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