What Can Affect California DUI Blood Test Results?

The legal limit for DUI in California is a blood alcohol concentration (“BAC”) of .08% or higher. At this BAC level, you are automatically presumed to be impaired by the alcohol in your system. However, you do not have to have a BAC above the legal limit to be charged with driving under the influence.

DUI Blood Testing: How to Challenge the Results in Your DUI Case

California uses a variety of tests to determine the BAC in a driver’s system. Breath and blood tests are the most common chemical tests for DUI. However, numerous conditions and factors could affect California DUI blood test results. If the police charge you with driving under the influence, contact a Southern California DUI lawyer for a free consultation to discuss potential DUI defenses and ways that you can challenge the results of a chemical blood test for BAC levels.

How Does a DUI Blood Test Work?

A qualified technician must perform blood tests in a DUI case. After a DUI arrest, the officer informs you that you must take a chemical test as required by California’s implied consent law (California Vehicle Code §23612). The officer explains that you must provide either a breath sample or a blood sample for chemical testing. Urine tests are only used when breath and blood samples cannot be obtained.

A technician uses an alcohol swab to clean your arm before drawing the blood. Then, the blood is sent to a lab for testing. There are precise rules which must be followed in the DUI Blood Test process.

Are DUI Blood Tests Reliable?

When a blood sample is taken, preserved, and tested correctly, it can be one of the most reliable ways to determine the amount of alcohol in your blood. The test detects the actual chemical content of the blood. Breathalyzers use a formula to estimate the BAC level based on the amount of alcohol on a person’s breath.

What Can Affect a Blood Alcohol Test and Cause a False BAC (Blood Alcohol Concentration) Result?

Blood tests can result in inaccurate results. Many factors could impact the results of a blood alcohol test. Some factors that could result in an inaccurate BAC result from a blood test include:

• The blood sample fermented before performing the BAC test;
• The blood draw was performed too long after the DUI arrest resulting in rising alcohol levels;
• The use of alcohol swabs to clean the areas before drawing blood;
• Certain health conditions of the person being tested;
• Failure to use a vial with the correct amounts of anti-coagulant and preservative;
• Using expired preservatives and/or anti-coagulants; and
• The blood sample was improperly collected and/or stored.

Because factors can result in inaccurate DUI blood test results, it is always in your best interest to discuss your DUI case with a Los Angeles DUI attorney before pleading guilty or accepting a DUI plea bargain.

Frequently Asked Questions About DUI Blood Tests in California

Because law enforcement officers almost always ask the driver for a blood sample, drivers often have questions about a blood draw after a DUI arrest. Below are answers to some of the most common FAQs about California DUI blood tests.

Can I Have a Lawyer Challenge My DUI Blood Test?

Yes, a Southern California DUI attorney can challenge the results of chemical testing for BAC levels. Whether you have grounds to contest the results depends on the facts of your case. Contact an expert DUI lawyer for a free consultation. A judge may exclude test results that could be inaccurate. The state would then need to prove you were intoxicated while driving a motor vehicle.

Can I Have a Different Laboratory Test the Blood Sample?

Title 17 of the California Code of Regulations provides the procedures for drawing, testing, and storing blood samples for DUI cases to comply with California Vehicle Code §23158.

In 17 CCR §1219.1, the regulations require that technicians collect a sufficient blood sample to provide for multiple tests. Individuals have up to one year after collecting their blood to request a sample for independent testing.

If you hire a defense attorney, they should request a portion of your blood to have it retested at an independent laboratory. If the prosecution refuses the request, the attorney files a “blood split motion” with the court asking for an order compelling the prosecutor to provide a sample of the blood for independent testing.

What if the Technician Used an Alcohol Swab Before the Blood Test? Can Alcohol Swab Affect Blood Alcohol Test?

Using an alcohol swab to clean the areas before drawing blood can impact the results of the test. Technicians violate Title 17 regulations if they use alcohol or a similar product to clean the area before a blood draw. Instead, technicians must use a non-alcoholic disinfectant to prep the skin for drawing blood.

How Long Does Blood Work Take to Come Back for Alcohol?

Several factors impact the timeline for blood work to come back from a lab. The lab’s backlog of tests is often the deciding factor in how long it takes to get results. It typically takes four to eight weeks to receive the results of a BAC test. However, it could take much longer if there are problems with the sample or the lab has a backlog of samples to test. The same is true with private laboratories that a California DUI defense lawyer might use to perform independent testing of DUI blood samples.

The results of breath tests are instant. However, officers do not preserve a sample of your breath. Therefore, there is no way to perform an independent test on the breath sample you provided after your DUI arrest.

Is Refusing a Blood Test a Good Idea or a Bad Idea? What Happens if I Refuse Chemical Testing?

It depends on the situation. Most people do not refuse a chemical test because there are penalties for refusing testing after a lawful DUI arrest. However, many drivers choose a breath test because it is less invasive than a blood test. Unfortunately, a breath test has a higher chance of being inaccurate than blood testing.

Why Is Attacking the Blood Test Results Such a Big Deal?

California Vehicle Code §23152 makes it illegal to drive with a blood alcohol content above the legal limit of .08%. It also makes it unlawful to operate a motor vehicle under the influence of alcohol or drugs. It is much easier for the state to prove you are guilty of drunk driving when it has test results showing your BAC exceeded the limits set by law.

Without the results of a blood test, the prosecutor must prove that you were “impaired” by alcohol or drugs in your system. Being impaired means you cannot operate the vehicle with the same level of care as a reasonably cautious sober person. Because impairment is a subjective conclusion, obtaining a DUI conviction without proof that the person’s BAC was above the legal limit can be more challenging.

Can I Still Fight the Blood Test if I Was Drinking or Using Drugs?

It is common for California DUI lawyers to challenge blood tests even if their client was drinking or using drugs. Again, for DUI charges, the state must prove your guilt beyond a reasonable doubt. Officers must follow regulations and statutes for chemical testing after a DUI arrest. Any slight error or deviation could be grounds for calling into question the results of a BAC test. The case might come down to expert witnesses testifying during a trial with differing opinions about whether the test results were accurate or inaccurate. Jurors would have to decide what to accept as fact.

When Is a DUI Blood Test Required in California Law?

Drivers are required to provide samples for testing after they are lawfully arrested for driving under the influence or DUI per se. Generally, the driver must choose between providing a blood or breath sample. However, there are exceptions to the rule.

For example, an officer can require a blood test if there is reasonable suspicion that the driver is under the influence of drugs. Also, the officer may require a blood sample when the driver is unconscious or deceased. Drivers taken to medical facilities that do not have breath testing equipment might be required to provide a blood sample.

Is It Better to Take a DUI Blood Test or Breath Test?

Breath tests are less invasive and faster, so many drivers choose a breathalyzer test. They blow into the mouthpiece to provide the breath sample. However, not everyone can provide a deep lung air sample required for a breathalyzer test’s accuracy. They might be unconscious or have a health condition that prevents them from breathing deeply.

Other drivers prefer a DUI blood test because they know that it measures the alcohol in their system instead of estimating BAC levels. Partition ratios are crucial components of the breathalyzer test, and the ratios are set by law. However, a driver may have a different partition ratio, which could impact the test results. Furthermore, breath samples cannot be preserved for retesting like blood samples.

What are the Title 17 Regulations?

Title 17 regulations refer to Title 17 of the California Code of Regulations. It provides detailed rules and procedures for collecting, testing, and storing chemical test samples. Violations of any of the provisions by officers, technicians, or labs could result in inaccurate test results. It could also give the court grounds to make the DUI test results inadmissible in court.

Are Blood Test Results Presumed to Be Valid?

There is a presumption that the results of a blood-alcohol test are accurate. In other words, the defendant has the burden of proving that the results are inaccurate. Title 17 procedures are often used to challenge the results of a test. However, a judge could find that the defendant’s constitutional rights were not violated. If so, the judge may allow the test results to be used as evidence during the trial even though there were violations of Title 17 regulations.

Forced Blood Draws – Can the Police Force a Person to Take a Blood Test?

There are very few cases where a person’s blood can be taken without a warrant. In the case of Birchfield v. North Dakota, the United States Supreme Court ruled that a warrantless breath test did not violate a person’s Fourth Amendment rights. However, warrantless blood tests do.

The case only applies when a state makes it a crime to refuse a blood test after a DUI arrest. California does not criminalize refusing a chemical test. Instead, the California Department of Motor Vehicles (“DMV”) administratively suspends a person’s driver’s license. The person only faces an enhanced penalty for test refusal if convicted of drunk driving.

A judge may issue a warrant for a blood sample resulting in a forced blood draw. A person can be physically forced to provide a blood sample if the police have a warrant.

Should I Hire a Lawyer to Dispute My Blood Test Results? 

If the police arrest you for driving under the influence, it is always in your best interest to call a Southern California DUI attorney for a free consultation. There could be one or more valid grounds for challenging the blood test results that could result in a dismissal or acquittal. You won’t know until you talk with an experienced defense lawyer.

Talk To A DUI Defense Attorney

You may have defenses to felony charges or may be able to get them reduced to a misdemeanor or “wet reckless” charges. An experienced attorney can evaluate your case and discuss your options with you. A lawyer serving DUI clients will often offer a free no obligation consultation and everything discussed is protected by the attorney client relationship.

Schedule a free consultation with one of our expert California DUI attorneys here.

Sources:

https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=VEH&sectionNum=23612

https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=VEH&sectionNum=23158.

https://govt.westlaw.com/calregs/Document/I9F4B2C835A2011EC8227000D3A7C4BC3?viewType=FullText&originationContext=documenttoc&transitionType=CategoryPageItem&contextData=(sc.Default)

https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?sectionNum=23152.&lawCode=VEH

https://www.oyez.org/cases/2015/14-1468

The Only 3 Effective DUI Field Tests

Police officers use field sobriety tests (“FSTs”) when they stop a driver suspected of being under the influence of drugs and/or alcohol. The three standardized field sobriety tests (“SFSTs”) are considered the most reliable FSTs and the tests recommended by the National Highway Traffic Safety Administration for use by law enforcement agencies. However, police officers also use non-standardized field sobriety tests. Unfortunately, all tests have potential issues that can make the results unreliable.

The Purpose and Types of DUI Field Sobriety Tests

How do police officers use field sobriety tests during DUI investigations in California?

California uses the three standardized field sobriety tests to conduct DUI investigations during traffic stops. The purpose of conducting the tests is to determine whether a driver is impaired. The tests also serve to provide probable cause for a DUI arrest. A police officer must have probable cause to believe the person is intoxicated before making a lawful DUI arrest.

Three tests were chosen as standardized field sobriety tests. Each test has specific instructions and procedures for giving the test to a driver. Any deviation from the procedures could make the test results inaccurate and unreliable. Those three tests are: (1) Horizontal Gaze Nystagmus Test (“HGN”); (2) Walk and Turn Test (“WAT”); and (3) One-Leg Stand Test (“OLS”).

Horizontal Gaze Nystagmus Test (“HGN”)

The Horizontal Gaze Nystagmus Test checks for involuntary “eye jerking” or nystagmus, which occurs when a person looks to the side without turning their head. The severity of the “jerking” increases when a person is intoxicated. An HGN test can also detect when a person has consumed certain prescription medications and illegal drugs.

The police officer performs the test by instructing the person to focus on a stimulus, which is usually a small object, finger, or pen. The officer moves the stimulus horizontally across the person’s line of sight about a foot to 15 inches away. As the driver’s eye follows the object, the police officer watches for signs of increased nystagmus including:

• Inability to follow the object smoothly;
• Distinct jerking at maximum deviation; and
• Substantial eye jerking within a minimum of 45 degrees from the center.

The officer looks for the signs in each eye, checking for six total signs of increased nystagmus.

Walk and Turn Test (“WAT”)

The Walk and Turn Test is the test most people are familiar with due to its depiction in movies and television. During the WAT, a police officer instructs the driver to take nine steps along a straight line, turn around, and then take nine steps back to the starting point. The steps must be heel-to-toe steps.  The officer instructs the driver to count the steps out loud as they take each step. The officer watches for eight indications that the person might be impaired:

• Inability to balance while listening to instructions;
• Making an improper turn;
• Beginning to walk before the officer instructs the person to begin the test;
• Taking the wrong number of steps;
• Stopping to regain balance while walking;
• Stepping out of line;
• Failing to touch the heels to the toes; and
• Using the arms for balancing.

The standardized instructions state that if the person displays at least two of the eight indicators, they fail the walk-and-turn test.

One-Leg Stand Test (“OLS”)

The police officer instructs the person to stand still and lift one foot off the ground about six inches. The officer instructs the person to count by one until the officer tells them to stop while holding their foot off the ground. The standardized instructions state the officer should time the suspect and stop them in 30 seconds. The officer looks for four indicators of impairment:

• Hopping during the test;
• Repeatedly swaying during the test;
• Putting their foot down one or more times; and
• Using the arms to maintain balance.

The standardized instructions state that committing two or more of the four indicators means the person failed the one-leg stand test.

Field Sobriety Tests: Potential Problems and Challenges

Even though the above tests are widely considered reliable indicators of driving under the influence, there are many problems with the tests. Critics cite issues with the accuracy and reliability of test results. They also question environmental factors and the actions of police officers that could result in flawed test results.

What Do the Tests Mean if You Fail?

The police officer should refer to their FSTs training to determine if the person “failed” a field sobriety test. As indicated above, specific instructions in the training materials indicate when a person has “failed” the test.

If the officer decides that you failed one or more of the FSTs, the officer will likely state they have probable cause for a DUI arrest. The officer may then ask the driver to take a preliminary alcohol screening (“PAS”) test, which is generally a field breathalyzer machine. A BAC (“blood alcohol content”) level on the breathalyzer gives the officer additional probable cause to make an arrest for DUI.

After a lawful DUI arrest, California’s implied consent laws require individuals to take a chemical test. The police officer should ask the person whether they want to provide a sample for a breath test or a blood test for chemical testing. Urine tests are only used when blood and breath tests are unavailable.

Field Sobriety Tests: Accuracy, Limitations, and Criticism

There are limits to using field sobriety tests during a DUI stop. There are also questions regarding the accuracy of field sobriety tests. Some of the issues that DUI defense attorneys raise regarding the use of FSTs in DUI cases include:

• The accuracy of field sobriety tests;
• Failing to provide clear and correct instructions;
• Environmental factors;
• Medical conditions;
• Being nervous &/or scared; and
• The subjectivity of SFSTs.

The Accuracy of Field Sobriety Tests

Several studies have been conducted on the accuracy of FSTs in determining whether a driver is impaired by alcohol and/or drugs. The NHTSA Instructor Guide for the tests explains that three studies were conducted between 1995 and 1998. The studies were conducted in San Diego, Florida, and Colorado. Each study resulted in different conclusions regarding the accuracy of FSTs.

The Instructor Manual states that officers should use the San Diego Field Validation Study when testifying in court. That study indicated the following accuracy rates:

• HGN tests were 88% accurate;
• OLS tests were 83% accurate; and
• WAT tests were 79% accurate.

Even though the NHTSA claims that the study results provide clear evidence of the validity of standardized field sobriety tests, California DUI defense lawyers disagree. First, these tests are not 100% accurate. Moreover, other scientific tests have shown that the accuracy of these tests is questionable.

One study used sober individuals to perform standardized FSTs. After watching videos of people taking the tests, police officers believed that a significantly larger number of the people were impaired. Another study concluded that the HGN test has a high baseline error and varied greatly depending on whether the person’s BAC level was rising or falling. In 52 videos of DUI arrests, the study authors concluded the HGN test was incorrectly administered 51 times.

Additionally, other factors make the accuracy and validity of the tests questionable.

Failing to Provide Clear and Correct Instructions

The police officer administering the SFSTs must follow the exact procedures for giving the test to a driver. Deviation from the procedures could result in inaccurate results. However, suppose there is no body camera footage, other video footage, or audio evidence that the officer gave the person clear and correct instructions. In that case, there is no way to know if the officer purposefully or unintentionally caused the person to “fail” the field sobriety test.

Environmental Factors

Numerous environmental factors could invalidate the results of standardized field sobriety tests. For example, the officer should conduct the tests on a level, paved surface. Otherwise, the person may stumble or lose their balance because of the ground, but not because they are impaired by alcohol. Another example is conducting the HGN test with bright lights shining in the person’s eyes from the sun or oncoming traffic. The lights could cause unreliable results.

Medical Conditions

Another problem to consider is the person’s health condition. A person may have a medical condition that prevents them from passing the test even though they are sober. In addition, a person’s age could cause them to perform poorly on a test even though they are perfectly capable of operating the motor vehicle safely. Physical limitations may prevent someone from “passing” the one-leg stand test or the walk-and-turn test.

Some medications could cause a person to exhibit signs of intoxication even though they are sober and not impaired. For example, some medications for seizures can cause increased nystagmus even though the person is sober. In addition, there are dozens of other possible causes of nystagmus, including hypertension, eye strain, glaucoma, and consuming excessive amounts of caffeine.

Being Nervous and Scared

Merely being nervous about being pulled over and scared of being arrested could cause someone to perform poorly on SFSTs.

SFSTs are Subjective

Whether you fail or pass a sobriety test depends upon the officer’s interpretation of your performance during the tests. In other words, one officer might conclude you were intoxicated and arrest you for drunk driving. Another police officer might conclude that you are not impaired and release you without an arrest. A study conducted using police officers, bartenders, and university community members found that the group had less than a 25% accuracy rate when correctly determining how drunk a person was after observing the targets for several minutes. Furthermore, the accuracy of the ratings worsened as the targets’ level of intoxication increased.

If a police officer has some bias against the person, the officer might unethically or unconsciously interpret the results in favor of probable cause and an arrest. For example, a driver was rude and obnoxious when the officer made the initial traffic stop. The person was critical and uncooperative. In that case, the officer might decide that the person is drunk and make the arrest, even though the results of the SFSTs were borderline.

Non-Standard Field Sobriety Tests

Some jurisdictions also use non-standardized field sobriety tests to determine impairment to support probable cause for a DUI arrest. Police officers claim the non-standard FSTs are reliable because they require the person to utilize split focus and dexterity, which is difficult to do if the person is drunk or drugged. However, these non-standardized tests are unreliable and highly subjective. Some non-standard field sobriety tests used by police officers include:

• Romberg Balance Test – Closing the eyes and tipping the head backward while standing with the feet together, estimating when 30 seconds have passed, and then saying “stop” to the officer.
• Finger-to-Nose Test – Closing the eyes and touching a finger to the tip of the nose.
• ABC Test – Reciting the alphabet forwards or backward.
• Finger-Tap Test – Tap a finger to your thumb as fast as possible with an opening between taps as wide as possible.
• Numbers Backward Test – Counting backward.
• Stand and Gaze Test – Standing and leaning so that the person gazes at the sky while holding their arms to their sides.
• Hand Pat Test – Extend an arm out with the palm facing up and out. Place the other hand on top of the raised palm facing down. Rotate the hands 180 degrees to pat the bottom hand with the back of the other hand before rotating and doing it again while counting “one” and “two” each time.

The NHTSA does not recognize these tests as reliable indicators of whether a person is impaired by alcohol and/or drugs. A skilled California DUI defense attorney will challenge these test results in court. Challenging non-standard field sobriety tests is easier because they are not widely accepted as accurate indicators of intoxication or impairment.

Field Sobriety Test Refusals – Drivers Aren’t Required to Participate in Field Sobriety Tests

No California law punishes a person for refusing to take a field sobriety test. However, a police officer will not tell you this detail. Instead, the officer will only ask you to perform the tests without indicating that you may refuse the test without punishment. Understanding your right to refuse to take a field sobriety test is essential because sober people can fail the tests.

However, there is a difference between field sobriety tests and chemical tests for BAC levels. California’s implied consent laws require drivers to submit to a chemical test of their blood or breath after a lawful DUI arrest. Refusing a chemical test after a DUI arrest results in an administrative driver’s license suspension by the California Department of Motor Vehicles (“DMV”). Your driving privileges are suspended for one year for a first-time refusal of a chemical test. A second refusal within ten years results in a two-year revocation of your driver’s license.

However, if you are under 21 years old or on probation, refusing a chemical test after a DUI arrest of a preliminary alcohol screening (“PAS”) test after being detained results in a one-year driver’s license suspension for the first refusal and two-year revocation for a second refusal within ten years.

California Vehicle Code §23612 states that an officer must advise you that refusing the chemical test could result in a suspension of your driving privileges. Your California DUI attorney might be able to successfully argue against the DMV administrative license suspension if the officer failed to provide the required advisements.

How Field Sobriety Test Results Are Used in Court & Challenging FSTs Results in California

The prosecution uses the results from field sobriety tests in court in several ways. First, the prosecutor may use the FSTs to support the finding that the police officer had probable cause to arrest you for driving under the influence.

If you are charged with driving under the influence, the prosecutor uses field sobriety tests to support the allegation that you were too impaired to drive. This situation often occurs when the driver refuses to take a chemical test. The state does not have evidence of the BAC level at the time of the arrest. Therefore, it must prove that your ability to operate the vehicle was impaired.

When you are charged with DUI per se, the state has BAC test results showing that you were driving with a BAC over the legal limit. Generally, the BAC test results are sufficient to prove the state’s case if there is no valid DUI defense to convince the jury you were not drunk or under the influence of drugs. However, a prosecutor might use the FSTs results as additional evidence you were drinking and driving.

A skilled California DUI lawyer challenges the results of standardized FSTs in court. The attorney might challenge the results in one of several ways including:

• Challenging the reliability of the tests based on data showing a considerable margin for error. The attorney might hire an expert witness to provide testimony regarding the accuracy of the test.
• Providing evidence that the law enforcement officer failed to administer the standard FSTs according to the procedures in the NHTSA manual.
• Offering evidence proving that the test results were negatively impacted by a medical condition, legal prescription medications, or environmental factors.
• Your clothing, lack of sleep, muscle fatigue, advanced age, injuries, weight, or other extraneous conditions caused poor performance on the FSTs.
• The officer administered non-standardized field sobriety tests.

There could be other challenges and DUI defenses in your case. Schedule a free consultation to talk with a DUI lawyer about potential defenses to drunk driving charges.

Talk to a California DUI Defense Attorney

Fighting DUI charges begins with hiring an experienced DUI defense attorney. Contact a criminal defense lawyer for a free consultation to discuss your case. Most attorneys offer a free consultation so that you can get answers to your questions about DUI defense and your legal rights to make an informed decision about how you want to proceed with your DUI case.

Schedule a free consultation with one of our expert California DUI attorneys here.

Interested in this topic or want to learn more about DUIs in California? Check out our blog, which is updated regularly!

Sources:

https://www.ojp.gov/ncjrs/virtual-library/abstracts/standardized-field-sobriety-testing

https://www.nhtsa.gov/sites/nhtsa.gov/files/documents/sfst_ig_refresher_manual.pdf

https://pubmed.ncbi.nlm.nih.gov/7991338/

https://pubmed.ncbi.nlm.nih.gov/11393940/

https://psycnet.apa.org/record/1984-12497-001

https://www.dmv.ca.gov/portal/driver-education-and-safety/dmv-safety-guidelines-actions/driving-under-the-influence/

https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=VEH&sectionNum=23612

Law enforcement officers rely heavily on field sobriety tests (FSTs) in California to determine if a driver is impaired by alcohol or drugs during a traffic stop. The FSTs may be the only “evidence” an officer collects during a DUI investigation to justify an arrest for driving under the influence. The theory is that poor performance on field sobriety tests indicates alcohol or drug impairment. 

However, these “standardized” field sobriety tests are not perfect. Even if the conditions are ideal and the police officer administers the FSTs precisely as directed by the NHTSA guidelines, the results of field sobriety tests can be inaccurate. According to the Instructor Guide provided by the National Highway Traffic Safety Administration, the accuracy levels for the FSTs are:

• Walk and Turn Test – 79% accurate
• One Leg Stand Test – 83% accurate
• Horizontal Gaze Nystagmus Test – 88% accurate

California drivers need to understand their rights regarding field sobriety tests. For example, a California driver does not have to take the field sobriety tests when stopped for suspicion of drunk driving.

California Drivers Can Refuse to Take Field Sobriety Tests

If you are pulled over for drunk driving, the police officer will ask you to take the field sobriety tests. He is looking for signs of impairment based on your performance on the FSTs. California does not impose any penalty for refusing to take field sobriety tests during a traffic stop.

As experienced DUI defense lawyers, we generally recommend that California drivers respectfully decline to take field sobriety tests for several reasons. Primarily, a sober person can fail a field sobriety test for reasons that have nothing to do with alcohol or drugs in their system. 

Unlike chemical tests (i.e., urine, blood, or breath test) that determine your blood alcohol content (BAC), the field sobriety test the officer gives you is a subjective review of “signs” that could indicate you are a drunk driver. The officer may have already made up his mind about arresting you for drunk driving. Taking the FSTs gives the police officer additional “evidence” to present to the court that justifies the DUI charges.

Failing field sobriety tests could result in one or more charges under the California Vehicle Code, including driving under the influence and DUID (driving under the influence of drugs).

To help you understand how California field sobriety tests work and how the results can be incorrect, we discuss the standardized FSTs and some non-standard field sobriety tests used by California police officers during a DUI stop.

DUI Field Sobriety Tests Used in California

As discussed above, the NHTSA has approved three field sobriety tests to be used by police officers during a roadside DUI investigation. The NHTSA considers these tests to be good indicators of a person’s impairment. 

The NHTSA bases its “validation” of these tests in part on a study by the Sand Diego Police Department. The study reported a strong connection between poor performance on these tests and alcohol or drug impairment. The tests are collectively referred to as the “standardized FSTs.” 

The Walk and Turn Test (WAT Test)

This divided attention test requires a person to simultaneously concentrate on a physical and mental task. For the test to be accurate, the police officer must give the person exact instructions for completing the test. The person must remember the instructions and complete them in order correctly.

Generally, the police officer tells the person to take nine heel-to-toe steps in a straight line (either a line on the road or an imaginary line). After completing nine heel-to-toe steps, turn around and take nine heel-to-toe steps back to the beginning point.

There are eight signs that the police officer may notate that could indicate the person is intoxicated or under the influence of drugs:

• Starts walking too soon
• Cannot maintain balance during the instructions
• Fails to walk in a heel to toe fashion
• Uses the arms to balance 
• Takes the wrong number of steps
• Stops while walking
• Steps off the line
• Fails to make the turn correctly

This FST has a 79% accuracy rating for indicating a BAC of .08 or greater because of poor performance. There could be many reasons why a person is unable to maintain balance while walking heel to toe.

The Horizontal Gaze Nystagmus Test (HGN Test)

Nystagmus is the involuntary movement or “jerking” of the eyes from side to side, up and down, or in a circle. Horizontal nystagmus describes the uncontrollable and rapid movement of the eyes from side to side. 

The HGN test given during a roadside field sobriety test involves the police officer noting the angel of the eye when it begins to “jerk” (exhibit nystagmus) as it moves side to side. The officer performs the test by moving a stimulus, such as a pen, from left to right and instructing the person to follow the object with their eyes.

Nystagmus at or before the 45-degree angle of the eye movement is associated with a high level of alcohol in the person’s system. However, the accuracy level of the HGN test is roughly 88%, according to the NHTSA. Therefore, the results of this field sobriety tests could be incorrect in at least 12% of the cases.

The One Leg Stand Test (OST Test)

This field sobriety test is another divided attention test used during a DUI traffic stop. While this test has a better accuracy rating according to the NHTSA, it still leaves a lot of room for errors.

During the OLT test, the police officer instructs the person to lift their foot about six inches off the ground. While holding that position, count from 1001 to 1030 and then look down at their foot.

Signs of impairment that the officer looks for during the test include swaying, hopping, using the arms to balance, and putting the foot down before completing the test.

Non-Standard DUI Field Sobriety Tests Used by Police Offices

In addition to the “standardized” field sobriety tests, police officers use various non-standard field sobriety tests during a DUI stop. The NHTSA has not approved or validated these tests because there is little to no evidence that poor performance on these tests indicates DUI impairment. Furthermore, the way the tests are administered can vary significantly from one law enforcement officer to another, increasing the chance that the test results are inaccurate. 

Several “signs” the officer looks for when performing these non-standard FSTs include:

• Ability to follow instructions, including counting correctly, starting and stopping correctly, and remembering instructions 
• Ability to balance and stand still
• Muscle tone and body/eye tremors
• Depth perception 
• Uttering unusual phrases or sounds
• Lack of muscle control
• Ability to perform mental and physical tasks simultaneously 

Some of the non-standard field sobriety tests used by California police officers include:

Finger Count Test

The police officer instructs the person to extend their hand with the palm facing upward in front of their body. Then, touch the top of the thumb to each finger, beginning with the index finger and working their way over to the little finger. While touching each finger, the person should count from one to four aloud. Then, the process is reversed for a total of three sets. 

Finger to Nose Test

This non-standard FST is one of the most common field sobriety tests officers perform. First, a police officer instructs the person to stand with their feet together and their arms at their sides. Then, after making a fist with each hand and keeping the index finger extended, the person must tilt their head back and close their eyes. 

The officer then instructs the person to extend either the left or right arm in front of their body and use their index finger to touch their nose. If the person cannot perform the test correctly, it is thought to be a sign of intoxication because the person lacks muscle control and coordination.

Romberg Balance Test

A police officer instructs the person to stand with their feet together, and their head tilted slightly backward. Then, with their eyes closed, the person must estimate when 30 seconds have passed. Finally, when they believe 30 seconds have passed, they will tilt their head forward, open their eyes, and say stop.

Hand Pat Test

The officer instructs the person to extend either the left or right hand in front of their body with the palm facing upward. Then, place their other hand on the top of that hand with the palm facing down. 

Keeping the bottom hand in the same location, the person must use the top hand to “pat” the bottom hand while counting “one, two, one, two, etc.” In addition, the person must rotate their top hand on each of the counts so that they pat their bottom hand palm down on the “one” counts and palm up on the “two” counts.

What Can Affect the Accuracy of a DUI Field Sobriety Test?

Many things can affect the accuracy of DUI field sobriety tests. For example, there are several medical reasons why a person would exhibit signs of nystagmus, including multiple sclerosis, head injuries, certain medications, and cataracts. 

Numerous physical and mental conditions may affect the accuracy of a test. Age, weight, inner ear problems, mental disabilities, anxiety, physical pain, and illness are just a few examples of why a person could “fail” a field sobriety test when they are not impaired by alcohol or drugs. In addition, being tired, having muscle fatigue from work or exercise, and stress can negatively impact a person’s ability to perform field sobriety tests correctly.

Weather and field conditions can have a significant impact on FST results. For example, if the test is given on an uneven surface, it increases the chance the person will lose their balance. In addition, bright lights from oncoming traffic and noise can affect test results.

The police officer’s conduct can result in inaccurate test results. For example, if the police officer does not provide clear instructions, the person may “fail” the test. Likewise, if the officer moves around, it can distract the person and result in inaccurate test results.

Even something as simple as wearing high heels, tight clothing, or baggy pants could adversely affect a person’s performance on field sobriety tests.

Fighting the Results of DUI Field Sobriety Tests in California

If you are arrested for DUI in California, you should discuss your legal options with a DUI defense attorney before pleading guilty to driving under the influence. There may be one or more grounds for challenging field sobriety tests.

When you are stopped for driving under the influence, an officer may have you perform one or more field sobriety tests. The purpose of these tests is to determine whether you are under the influence of drugs or alcohol. The National Highway Traffic Safety Administration (NHTSA) has approved and standardized three field sobriety tests for use during DUI investigations:

• HGN (horizontal gaze nystagmus) test
• Walk and turn test
• One-leg stand test

Many police officers use the “finger-to-nose” test during DUI investigations. However, this test is an unofficial field sobriety test that the NHTSA does not approve. As such, several issues can arise when a police officer uses the finger-to-nose test as part of a DUI investigation. 

What is the Finger-to-Nose Test?

A police officer instructs you to close your eyes and slightly tilt your head backward. Then, with your index finger, you touch the tip of your nose. The police officer has you repeat the process three times with each hand. Before each attempt, the police officer informs you which hand to use to touch the tip of your nose.

During the finger-to-nose test, a police officer observes you for signs of impairment. Specifically, the officer observes:

• Your ability to follow instructions during the test
• The direction and amount your body sways during the test
• Whether you have body, leg, or eyelid tremors
• Your depth perception and muscle tone
• Unusual sounds or statements you make during the test
• Whether you can touch your nose with your index finger or other parts of your face

Because the finger-to-nose test is not a standardized field sobriety test, police officers are not required to use specific procedures to instruct the person how to perform the test. Likewise, officers are not required to perform the test under specific conditions.

Therefore, the test can produce wildly inaccurate results because of a police officer’s subjective view of the suspect’s performance. A DUI defense lawyer may attack the validity and results of the finger-to-nose test on many points.

Field Sobriety Tests Used During a DUI Investigation

The three NHTSA standardized three field sobriety tests used during DUI investigations. Several scientific studies validate the correlation between performance during these tests and DUI impairment through statistical means. 

Police officers must follow strict and specific procedures for administering standardized field sobriety tests. Failing to follow the requirements for testing could make the results subject to challenge in court.

Even though the NHTSA only has three standardized DUI field sobriety tests, police officers often use several non-standard field sobriety tests during a DUI investigation. In addition to the finger-to-nose test, a police officer may use  the following tests to judge your impairment level during a DUI investigation:

Hand Pat Test

You extend your hand out in front of your palm up and then place your other hand on top of that hand palm down, as if you are about to start clapping. Then, counting “one, two, one, two, etc.,” you pat your hands together. Your bottom hand remains stationary. 

However, you turn the top hand from palm down to palm up between each movement. The result is that you “pat” your bottom hand with your top hand palm down on the “one” counts and palm up on the “two” counts.

Romberg Balance Test

During this test, you stand with your feet together and your head slightly tilted backward. Then, with your eyes closed, you must estimate when 30 seconds have passed. At that time, you tilt your head forward, open your eyes, and say stop.

Finger Count Test

The police officer instructs you to put one hand in front of you with your palm facing upward. You then touch your thumb to the tip of each finger, beginning with your index finger and ending with your little finger. As you touch each finger, you count from one to four. Then, the process is reversed and performed three times. 

As with standardized field sobriety tests, police officers observe your ability to follow instructions, coordination, balance, body tremors, and comments made during these non-standardized field sobriety tests. The purpose is to determine if you are impaired by alcohol or drugs.

However, the results of these non-standardized field sobriety tests are also highly subjective. The same problems exist with these tests as with the finger-to-nose test.

Using the Finger-to-Nose Test to Examine the Cerebellum and Measure Ataxia

The instructions provided for the finger-to-nose test are designed to help measure ataxia. Ataxia is the lack of muscle control or coordination of voluntary movements. It may be caused by alcohol use. 

The finger-to-nose test is supposed to detect a lack of voluntary coordination of voluntary muscle movements. A lack of coordination could indicate problems with the cerebellum, which could indicate intoxication. 

Because the finger-to-nose test is not a standardized test, the instructions police officers give to suspects can vary. However, general instructions include:

• Stand with your feet together and your arms down at your side
• Make a fist with each hand, keeping the index finger extended and turn your hand so your palm faces upward
• Tilt your head back slightly
• Close your eyes (closing your eyes before tilting your head back could impair normal equilibrium)
• Extend your right (or left) arm straight out in front of your body and then touch your index finger to your nose before returning your arm back down to your side

As you perform the test, the police officer watches for “clues” or indicators of neurological dysfunctions that suggest you may have been driving under the influence of drugs or alcohol. 

Specific “clues” the police officer notes include:

• Your inability to follow instructions, such as keeping your feet apart or extending the incorrect finger when making a fist.
• Being unable to stand still. You sway from side to side or back to front, so the police officer finds that your inability to maintain balance is a sign of impairment. 
• You exhibit the “shakes” because you involuntarily tremble when performing the test. Your muscle tone may appear more rigid or limp than is expected for a sober person.
• You utter unusual sounds or make statements that the officer believes indicate you are intoxicated, such as signing while performing the test or repeatedly stating you have to “pee.”
• You take too much time or you try too fast to touch your finger to your nose. Either action could indicate a problem with depth perceptions. 
• The officer notes whether you use the correct sequence for touching your nose that the officer gave you.

As stated above, the results of the finger-to-nose test are subjective. For example, an officer might believe that asking to use the bathroom is an unusual statement, while another officer might assume that you just need to urinate. Likewise, belching could be interpreted as being intoxicated, but it could result from having just eaten a large meal.

Therefore, the reliability of the finger-to-nose test can be questionable.

Challenging the Results of the Finger-to-Nose Test 

Because the NHTSA has not approved the finger-to-nose test, police officers do not have a specific list of criteria to use when determining if a person “fails” the test. Furthermore, the procedure for administering the test can vary significantly from one jurisdiction to another and even more from one officer to another. Therefore, the validity of the test and the accuracy of the results are subject to scrutiny.

Additionally, there are numerous reasons why a person could fail the finger-to-nose test that have nothing to do with intoxication. Conditions or circumstances that could impact the results of the finger-to-nose test include, but are not limited to:

• Ataxia caused by medications instead of being caused by alcohol intoxication. Certain medications may cause a lack of coordination of muscle movements, such as anti-seizure medications and medications for depression.
• Brain damage and neurological defects could negatively impact the function of the cerebellum, which may impact coordination. 
• Mental disabilities may prevent a person from understanding the instructions given by police officers when performing the finger-to-nose test.
• Roadside conditions could impact the results of the test. For example, load noises from traffic, flashing lists, and other distractions could be the cause of the “clues” of intoxication the officer notes instead of alcohol use.
• Incorrect sequences of instructions could impair the person’s equilibrium. Therefore, if a police officer tells the person to close their eyes and then tilt their head back, the test results could be invalid.

Without standardization, the results of a finger-to-nose test at a DUI stop can be inaccurate. Furthermore, without standard instructions to guide officers in judging the “clues” they observe during the test, it is impossible to know whether a police officer judged the person’s responses too harshly.

A DUI defense attorney can argue that the inherent defects in the finger-to-nose test make the results inconclusive, especially if there is no other evidence that the driver was intoxicated. 

Talk with a DUI defense lawyer if your DUI arrest was based partially on a finger-to-nose test. You may have a strong defense that could result in a dismissal of charges.

It is not uncommon for people arrested on suspicion of a California DUI to mistaken believe that it is in their best interest to flatly refuse the breathalyzer. Not knowing the correct thing to do in this scenario can be the difference between becoming convicted of a California DUI and not, and unfortunately, the right thing to do is a little more complicated than merely refusing the breathalyzer or not.

When people refer to a “breathalyzer” during a California DUI stop, they actually referring to two different tests. The first is the roadside breathalyzer, often called a preliminary screening alcohol test or “PAS” test, and the second is the “chemical breath test.”

According to California Vehicle Code section 23612(h), the PAS test “indicates the presence or concentration of alcohol based on a breath sample in order to establish reasonable cause to believe the person was driving [under the influence]…[it] is a field sobriety test and may be used by an officer as a further investigative tool.”

The PAS roadside breath test, like other field sobriety tests such as the walk-and-turn test, the horizontal gaze nystagmus test, and the one leg stand test, are optional. Although an officer might threaten to arrest someone for refusing the optional breathalyzers, a driver should stand their ground and politely refuse to complete any field sobriety tests. Despite what the officer might say, they are optional and are only meant to give the officer the evidence they need to arrest the driver.

In fact, the officer must advise the driver that the roadside breath test is optional. California Vehicle Code section 23612(i) states that “If the officer decides to use a [PAS], the officer shall advise the person that he or she is requesting that person to take a [PAS] test to assist the officer in determining if that person is under the influence. The person’s obligation to submit to a [chemical test under California’s Implied Consent Law] is not satisfied by the person submitting to a [PAS] test. The officer shall advise the person of that fact and of the person’s right to refuse to take the [PAS] test.”

As stated above, providing a breath sample to an officer during the PAS test only give the officer the evidence they need to arrest a driver. Whether a driver provides the officer that information or not, the officer will have to make the decision to arrest a driver on suspicion of a DUI or not. In order to arrest a driver on suspicion of a California DUI, the officer must have probable cause. The probable cause can consist of driving patterns indicative of intoxication, bloodshot eyes, slurred speech, smell of alcohol on a driver’s breath, admissions of drinking or intoxication, and, yes, a reading of the pass test indicating a BAC of 0.08 percent or higher.

If the officer meets the probable cause standard by obtaining and/or observing enough evidence that a driver is driving under the influence, the officer can lawfully arrest the driver on suspicion of driving under the influence. Once this happens, California’s Implied Consent law takes effect.

California’s Implied Consent law, codified in California Vehicle Code section 23612(a)(1)(A), “A person who drives a motor vehicle is deemed to have given his or her consent to chemical testing of his or her blood or breath for the purpose of determining the alcohol content of his or her blood, if lawfully arrested for an offense allegedly committed in violation of [California’s DUI laws].”

Simply put, if you have a license and you drive in California, you have impliedly consented to submit to the chemical test after you have lawfully been arrested for a DUI, which can either be a breath test or a blood test. If the driver opts not to give blood, then they must provide a breath test. Conversely, if a person opts against the breath test, they must submit to the blood test.

So should you pass on the breathalyzer?

Pass on the roadside “PAS” test. Submit to the chemical test required under California’s Implied Consent law (See Breath or Blood Test After a California DUI Stop).