Purpose of Field Sobriety Tests

Field sobriety tests are designed to provide officers with additional evidence to determine whether a driver is impaired by alcohol or drugs. The primary purpose of these tests is to help officers establish probable cause for an arrest if they suspect a driver is under the influence. FSTs are used in conjunction with other observations and tests, such as breathalyzers or blood tests, to build a case against the driver.

Types of Field Sobriety Tests

California law enforcement officers typically use three standardized field sobriety tests, which have been validated through research for their effectiveness in detecting impairment. These tests are:

1. Horizontal Gaze Nystagmus (HGN) Test:

The HGN test measures the involuntary jerking of the eyes as they follow a moving object, usually a pen or flashlight. Officers assess how well the driver’s eyes follow the object and look for signs of nystagmus, which can be indicative of alcohol impairment. The test is based on the premise that alcohol impairs the nervous system, affecting eye movements.

2. Walk-and-Turn Test:

In this test, the driver is asked to walk a straight line, turn, and walk back while following specific instructions. The officer observes the driver’s ability to maintain balance, follow directions, and walk in a straight line. This test assesses divided attention and physical coordination, which can be impaired by alcohol.

3. One-Leg Stand Test:

The driver is instructed to stand on one leg for a specified period, usually 30 seconds, while counting aloud. The officer observes the driver’s ability to maintain balance and follow instructions. Difficulty in performing this test may indicate impairment.

Effectiveness of Field Sobriety Tests

While field sobriety tests can provide useful evidence, their effectiveness is not without limitations. The standardized tests are designed to be relatively accurate, but they are not foolproof. Several factors can affect the reliability of FSTs:

1. Test Conditions: Environmental conditions, such as poor lighting, uneven surfaces, or inclement weather, can impact a driver’s performance on FSTs. These factors can make it difficult for drivers to perform the tests as required.
2. Individual Differences: Not all individuals are equally capable of performing FSTs, regardless of impairment. Factors such as age, physical health, and injuries can affect a person’s ability to complete the tests accurately. For instance, a person with a leg injury or balance issues may struggle with the walk-and-turn or one-leg stand tests.
3. Officer Training: The administration and evaluation of FSTs require proper training. Officers must follow standardized procedures to ensure accurate results. If an officer is not properly trained or deviates from established protocols, the results may be unreliable.

Challenges to Field Sobriety Tests

Field sobriety tests can be challenged in court on several grounds. Common challenges include:

1. Improper Administration: If the officer did not administer the tests according to standardized procedures, the results may be questioned. This includes issues such as not providing clear instructions or not conducting the tests in a safe and appropriate environment.
2. Medical Conditions: Medical conditions or physical disabilities can impact a person’s ability to perform FSTs. For example, conditions such as vertigo, arthritis, or neurological disorders can affect balance and coordination, making the results of FSTs unreliable.
3. Subjectivity: The interpretation of FST results can be subjective. Officers may have varying opinions on whether a driver’s performance indicates impairment. This subjectivity can be challenged by arguing that the officer’s observations were biased or inaccurate.
4. Environmental Factors: The conditions under which the tests are conducted can affect performance. Factors such as uneven ground, distractions, or weather conditions can all impact a driver’s ability to perform the tests correctly.

Legal Implications of Field Sobriety Tests

In California DUI cases, field sobriety test results can be used as evidence to support charges of driving under the influence. However, the results are only one part of the overall evidence considered in a DUI case. Other evidence, such as breathalyzer or blood test results, police observations, and witness testimony, also play a significant role.

The results of field sobriety tests may be used by the prosecution to argue that the driver was impaired, but they can also be challenged by the defense. A skilled DUI attorney can scrutinize the administration of the tests, identify potential issues, and use this information to challenge the validity of the evidence.

Conclusion

Field sobriety tests are a key component of DUI investigations in California, providing officers with additional evidence to assess a driver’s impairment. While these tests can be useful, they are not without limitations and can be subject to various challenges. Understanding the role of field sobriety tests, their effectiveness, and common issues associated with their use can help drivers better navigate the legal process if faced with DUI charges. Working with an experienced DUI attorney can also assist in effectively challenging the results and building a strong defense.