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Types of Field Sobriety Tests

Types of Field Sobriety Tests

Field sobriety tests (FSTs) are essential tools used by law enforcement officers to assess whether a driver is under the influence of alcohol or other intoxicating substances. These tests help officers determine probable cause for arrest and subsequent chemical testing. There are several types of field sobriety tests, each designed to measure specific physical and cognitive functions that are typically impaired by alcohol and drugs. Understanding these tests can provide valuable insight into the procedures and reliability of DWI assessments.

Standardized Field Sobriety Tests

The National Highway Traffic Safety Administration (NHTSA) has developed a standardized battery of three field sobriety tests that are widely used by law enforcement across the United States. These tests include:

  1. Horizontal Gaze Nystagmus (HGN)
    The HGN test involves observing the involuntary jerking of the eye as it follows a moving object, such as a pen or flashlight. During this test, the officer instructs the suspect to follow the object with their eyes while keeping their head still. The officer looks for three specific clues in each eye:
    • Lack of smooth pursuit
    • Distinct nystagmus at maximum deviation
    • Onset of nystagmus prior to 45 degrees

Nystagmus is a normal phenomenon, but when a person is intoxicated, the jerking becomes more pronounced and occurs at lesser angles. This test is considered highly reliable, with a high correlation to blood alcohol concentration (BAC) levels.

  1. Walk-and-Turn (WAT)
    The Walk-and-Turn test assesses a person’s ability to follow instructions and maintain balance. The suspect is instructed to take nine steps, heel-to-toe, along a straight line, turn on one foot, and return in the same manner. During the test, the officer observes eight possible indicators of impairment:
    • Inability to maintain balance during instructions
    • Starting before instructions are finished
    • Stopping while walking
    • Not touching heel-to-toe
    • Stepping off the line
    • Using arms for balance
    • Making an improper turn
    • Taking an incorrect number of steps

The WAT test evaluates both mental and physical faculties, making it an effective measure of impairment.

  1. One-Leg Stand (OLS)
    The One-Leg Stand test requires the suspect to stand on one leg while holding the other foot approximately six inches off the ground and counting aloud until told to stop. The officer looks for four indicators of impairment:
    • Swaying while balancing
    • Using arms to balance
    • Hopping to maintain balance
    • Putting the foot down

This test assesses the individual’s balance and coordination, which are often compromised when a person is under the influence.

Non-Standardized Field Sobriety Tests

In addition to the standardized tests, officers may use a variety of non-standardized tests to assess sobriety. These tests can vary widely and may include:

  1. Finger-to-Nose Test
    The suspect is asked to close their eyes, tilt their head back, and touch their nose with the tip of their finger. This test evaluates coordination and the ability to follow instructions.
  2. Alphabet Test
    The suspect is instructed to recite the alphabet from a specified starting point (e.g., from the letter ‘D’ to ‘P’). This test assesses cognitive function and memory.
  3. Counting Test
    The suspect may be asked to count backward from a specified number or count in a sequence (e.g., by twos). This test evaluates cognitive function and the ability to follow instructions.
  4. Rhomberg Balance Test
    The suspect is asked to stand with their feet together, tilt their head back, and estimate the passage of 30 seconds. This test assesses balance, timing, and internal clock function.

Reliability and Limitations

While field sobriety tests are valuable tools, they are not without limitations. Factors such as age, weight, medical conditions, nervousness, and environmental conditions can affect performance. Standardized tests, particularly the HGN, WAT, and OLS, are generally more reliable due to their structured nature and defined criteria for scoring. However, non-standardized tests may be more subjective and less reliable.

See Also

It is important for law enforcement officers to administer these tests consistently and accurately to ensure fair and reliable results. Proper training and adherence to protocols are essential to minimize errors and false positives.

Legal Implications

Field sobriety tests play a crucial role in the legal process of DWI cases. The results of these tests can provide probable cause for arrest and be used as evidence in court. However, the admissibility and weight of these tests can be challenged by Houston dwi defense attorneys, particularly if there are questions about the administration or conditions of the tests.

In conclusion, field sobriety tests are a critical component of DWI enforcement. Understanding the types and purposes of these tests can help individuals better navigate interactions with law enforcement and the legal system. Whether standardized or non-standardized, these tests aim to ensure that roads remain safe by identifying impaired drivers and preventing potential accidents.

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