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What are the standard field sobriety tests used by police in Florida?



Introduction to Standard Field Sobriety Tests (SFSTs) in Florida

Field Sobriety Tests (FSTs) are a series of standardized tests used by law enforcement officers to determine whether a driver is impaired. In Florida, these tests are crucial in DUI investigations and help officers establish probable cause for arrest. Understanding the different types of SFSTs and their procedures can be vital for anyone facing DUI charges.

History and Development of SFSTs

The National Highway Traffic Safety Administration (NHTSA) developed the SFSTs in the late 1970s. Extensive research was conducted to identify the most reliable and accurate tests for assessing impairment. The three primary tests that emerged from this research are the Horizontal Gaze Nystagmus (HGN), Walk-and-Turn (WAT), and One-Leg Stand (OLS).

What are Standard Field Sobriety Tests? Standard Field Sobriety Tests are a set of three tests developed by NHTSA to assess a driver’s impairment due to alcohol or drugs.

For many years, law enforcement officers have utilized field sobriety tests to determine the impairment of a person’s driving due to alcohol influence. The performance of the person on those field sobriety tests was used by the officer to develop probable cause for arrest and as evidence in court. A wide variety of field sobriety tests existed, and there was a need to develop a battery of standardized valid tests.

Beginning in late 1975, extensive scientific research studies were sponsored by NHTSA through a contract with the Southern California Research Institute (SCRI) to determine which roadside field sobriety tests were the most accurate. SCRI published the following three reports:

  • California: 1977 (Lab)
  • California: 1981 (Lab and Field)
  • Maryland, D.C., VA, N.C.: 1983 (Field)

SCRI traveled to law enforcement agencies throughout the United States to select the most commonly used field sobriety tests. Six tests were used in the initial stages of this study. Laboratory research indicated that three of these tests, when administered in a standardized manner, were a highly accurate and reliable battery of tests for distinguishing BACs above 0.10:

  • Horizontal Gaze Nystagmus (HGN)
  • Walk-and-Turn (WAT)
  • One-Leg Stand (OLS)

NHTSA analyzed the laboratory test data and found:

  • HGN, by itself, was 77% accurate
  • WAT, by itself, was 68% accurate
  • OLS, by itself, was 65% accurate
  • By combining HGN and WAT, an 80% accuracy can be achieved

The final phase of this study was conducted as a field validation. Standardized, practical, and effective procedures were developed. The tests were determined to discriminate in the field, as well as in the laboratory. The three standardized tests were found to be highly reliable in identifying subjects whose BACs were above 0.10. The results of the study unmistakably validated the SFSTs.

SFST Validation Studies

Three SFST validation studies were undertaken between 1995 and 1998:

  • Colorado – 1995
  • Florida – 1997
  • San Diego – 1998

The Colorado SFST validation study was the first full field study that utilized law enforcement personnel experienced in the use of SFSTs. The initial study utilized only a few experienced officers in DWI enforcement in both a laboratory setting and field setting. Correct arrest decisions were made 93% of the time based on the 3-test battery (HGN, WAT, OLS). This was substantially higher than the initial study results.

The Florida SFST field validation study was undertaken to answer the question of whether SFSTs are valid and reliable indices of the presence of alcohol when used under present-day traffic and law enforcement conditions. Correct decisions to arrest were made 95% of the time based on the 3-test battery (HGN, WAT, OLS).

The San Diego SFST validation field study was undertaken because of the nationwide trend towards lowering the BAC limits to 0.08. The question to be answered was, “Does SFST discriminate at BACs below 0.10?” Correct arrest decisions were made 91% of the time based on the 3-test battery (HGN, WAT, OLS) at the 0.08 level and above. The results of this study provide clear evidence of the validity of the 3-test battery. To support arrest decisions above or below 0.08, it strongly suggests that the SFSTs also accurately discriminate BACs at 0.04 and above.

For more information on how these tests are challenged in court, you can refer to our detailed guide on challenging HGN evidence and our comprehensive article on challenging the Walk-and-Turn test in DUI defense.

Horizontal Gaze Nystagmus (HGN) Test

The Horizontal Gaze Nystagmus (HGN) test is one of the most reliable field sobriety tests used by police in Florida. This test involves observing the eyes of the suspect as they follow a moving object, such as a pen or flashlight, horizontally. The officer looks for involuntary jerking of the eyes, which can indicate impairment.

What are the standard field sobriety tests used by police in Florida?

Procedure for HGN Test

The HGN test is a meticulous process that requires careful observation. Here’s a step-by-step breakdown of how the test is administered:

  1. Initial Positioning: The officer positions the suspect in a safe, well-lit area. The suspect is instructed to remove eyeglasses, if any, and to keep their head still while following a stimulus with their eyes only.
  2. Stimulus Presentation: The officer holds a stimulus, such as a pen or flashlight, approximately 12-15 inches from the suspect’s nose and slightly above eye level.
  3. Smooth Pursuit: The officer moves the stimulus horizontally across the suspect’s field of vision. The suspect’s eyes should follow the stimulus smoothly. If the eyes jerk or “bounce,” it is a sign of impairment.
  4. Maximum Deviation: The officer moves the stimulus to the maximum range of the suspect’s vision and holds it there for a minimum of four seconds. The presence of distinct and sustained nystagmus (eye jerking) is another indicator of impairment.
  5. Onset of Nystagmus: The officer moves the stimulus slowly towards the center, observing the angle at which nystagmus begins. If nystagmus occurs before the eye reaches 45 degrees, it suggests a BAC above 0.08.

These steps are critical in ensuring the accuracy and reliability of the HGN test. Each step provides specific clues that help the officer determine the suspect’s level of impairment.

What is Horizontal Gaze Nystagmus? Horizontal Gaze Nystagmus is an involuntary jerking of the eyes that occurs as they gaze to the side. It is a reliable indicator of alcohol impairment.

Scientific Basis of the HGN Test

The HGN test is grounded in extensive research and scientific validation. The National Highway Traffic Safety Administration (NHTSA) sponsored studies in the 1970s to identify the most accurate field sobriety tests. The HGN test emerged as a top contender due to its high reliability in detecting impairment.

According to NHTSA’s research:

  • Accuracy: The HGN test alone is 77% accurate in identifying individuals with a BAC above 0.10.
  • Combination: When combined with the Walk-and-Turn (WAT) test, the accuracy increases to 80%.
  • Validation Studies: Subsequent field validation studies in Colorado, Florida, and San Diego confirmed the test’s reliability under real-world conditions.

These findings underscore the importance of the HGN test in DUI investigations. Its scientific basis provides a robust foundation for its use in the field.

How accurate is the HGN test? The Horizontal Gaze Nystagmus test is 77% accurate in identifying individuals with a BAC above 0.10, making it one of the most reliable field sobriety tests.

Challenging HGN Test Results

Despite its reliability, the HGN test is not infallible. Various factors can affect its accuracy, and understanding these can be crucial in challenging the test results:

  • Medical Conditions: Certain medical conditions, such as neurological disorders or eye muscle fatigue, can cause nystagmus unrelated to alcohol impairment.
  • Environmental Factors: Poor lighting, moving vehicles, or other distractions can interfere with the test’s administration and affect the results.
  • Improper Administration: The test must be administered according to strict guidelines. Any deviation from the standard procedure can compromise the results.

Challenging the HGN test results requires a thorough understanding of these factors. An experienced DUI attorney can scrutinize the test’s administration and identify potential issues that may weaken the prosecution’s case. For more information on how to challenge HGN evidence, visit our page on challenging HGN evidence.

The results of the HGN test can have significant legal implications. If the test indicates impairment, it can provide probable cause for arrest and be used as evidence in court. However, the reliability of the test results can be contested on various grounds, including:

  • Officer Training: The officer administering the test must be properly trained and certified. Lack of proper training can be a basis for challenging the test results.
  • Documentation: Detailed documentation of the test’s administration and the suspect’s performance is crucial. Incomplete or inaccurate documentation can cast doubt on the test’s validity.
  • Expert Testimony: Expert witnesses can provide valuable insights into the test’s scientific basis and potential flaws. Their testimony can help challenge the prosecution’s evidence.

Understanding the legal implications of the HGN test results is essential for anyone facing DUI charges. For more insights into the legal challenges of field sobriety tests, explore our page on challenging the Walk-and-Turn test.

The HGN test is a critical component of DUI investigations in Florida. Its scientific basis and high accuracy make it a valuable tool for law enforcement. However, understanding its limitations and potential challenges is crucial for a robust defense. For more information on the effectiveness of field sobriety tests, visit our page on the effectiveness of the One-Leg Stand test.

Walk-and-Turn (WAT) Test

The Walk-and-Turn (WAT) test is another standardized field sobriety test used in Florida DUI investigations. This test assesses a suspect’s ability to follow instructions and maintain balance while walking in a straight line.

Procedure for WAT Test

The Walk-and-Turn test is designed to evaluate both mental and physical capabilities. Here’s how it works:

  1. Initial Instructions: The officer instructs the suspect to stand with one foot in front of the other, heel-to-toe, and arms at their sides. The suspect must maintain this position while the officer gives further instructions.
  2. Walking Phase: The suspect is then instructed to take nine heel-to-toe steps along a straight line, turn on one foot, and return in the same manner. The officer demonstrates the steps and turn to ensure the suspect understands.
  3. Observation: The officer observes the suspect for several indicators of impairment, including starting before instructions are finished, inability to maintain balance, not walking heel-to-toe, stepping off the line, using arms to balance, making an improper turn, and taking the incorrect number of steps.

This test requires a designated straight line and should be conducted on a reasonably dry, hard, level, and non-slippery surface. There should be sufficient room for suspects to complete the nine heel-to-toe steps. Common errors by Florida officers can impact the results of the test.

What is the Walk-and-Turn test? The Walk-and-Turn test is a standardized field sobriety test used to assess a suspect’s ability to follow instructions and maintain balance while walking in a straight line.

Indicators of Impairment

The Walk-and-Turn test includes several indicators that officers look for to determine impairment:

  • Cannot Keep Balance: The suspect fails to maintain the heel-to-toe position during the instruction phase.
  • Starts Too Soon: The suspect begins walking before the officer completes the instructions.
  • Stops While Walking: The suspect pauses during the walk.
  • Does Not Touch Heel-to-Toe: There is a gap of more than half an inch between the heel and toe on any step.
  • Steps Off the Line: The suspect steps off the designated line.
  • Uses Arms for Balance: The suspect raises one or both arms more than six inches from their sides to maintain balance.
  • Improper Turn: The suspect makes an incorrect turn, such as spinning or pivoting instead of taking a series of small steps.
  • Incorrect Number of Steps: The suspect takes more or fewer than nine steps in either direction.

These indicators are critical in assessing whether a suspect’s blood alcohol concentration (BAC) is above the legal limit. For more on how officers might make mistakes during these tests, visit our page on common mistakes in field sobriety testing.

How accurate is the Walk-and-Turn test? The Walk-and-Turn test is 68% accurate in identifying individuals with a BAC above 0.10, according to NHTSA research.

Scientific Validation of the WAT Test

The Walk-and-Turn test has been scientifically validated through extensive research conducted by the National Highway Traffic Safety Administration (NHTSA). Here’s a brief overview of the findings:

  • Initial Research: The Southern California Research Institute (SCRI) identified the WAT test as one of the most accurate field sobriety tests for distinguishing BACs above 0.10.
  • Accuracy: The WAT test alone is 68% accurate in identifying individuals with a BAC above 0.10.
  • Field Validation Studies: Subsequent field validation studies in Colorado, Florida, and San Diego confirmed the test’s reliability under real-world conditions.

These findings underscore the importance of the WAT test in DUI investigations. Its scientific basis provides a robust foundation for its use in the field. For more details on the accuracy of field sobriety tests, visit our page on the effectiveness of the One-Leg Stand test.

Challenging WAT Test Results

Despite its reliability, the WAT test is not infallible. Various factors can affect its accuracy, and understanding these can be crucial in challenging the test results:

  • Medical Conditions: Certain medical conditions, such as neurological disorders or injuries, can affect balance and coordination.
  • Environmental Factors: Uneven surfaces, poor lighting, or adverse weather conditions can interfere with the test’s administration.
  • Improper Administration: The test must be administered according to strict guidelines. Any deviation from the standard procedure can compromise the results.

Challenging the WAT test results requires a thorough understanding of these factors. An experienced DUI attorney can scrutinize the test’s administration and identify potential issues that may weaken the prosecution’s case. For more information on challenging field sobriety tests, visit our page on challenging the Walk-and-Turn test in DUI defense.

The results of the WAT test can have significant legal implications. If the test indicates impairment, it can provide probable cause for arrest and be used as evidence in court. However, the reliability of the test results can be contested on various grounds, including:

  • Officer Training: The officer administering the test must be properly trained and certified. Lack of proper training can be a basis for challenging the test results.
  • Documentation: Detailed documentation of the test’s administration and the suspect’s performance is crucial. Incomplete or inaccurate documentation can cast doubt on the test’s validity.
  • Expert Testimony: Expert witnesses can provide valuable insights into the test’s scientific basis and potential flaws. Their testimony can help challenge the prosecution’s evidence.

Understanding the legal implications of the WAT test results is essential for anyone facing DUI charges. For more insights into the legal challenges of field sobriety tests, explore our page on challenging HGN evidence.

The Walk-and-Turn test is a critical component of DUI investigations in Florida. Its scientific basis and accuracy make it a valuable tool for law enforcement. However, understanding its limitations and potential challenges is crucial for a robust defense. For more information on the role of field sobriety tests in DUI cases, visit our page on the role of field sobriety tests in court cases.


One-Leg Stand (OLS) Test

The One-Leg Stand (OLS) test is the third standardized field sobriety test used by police in Florida. This test evaluates a suspect’s balance and coordination by having them stand on one leg for a specified period. It is designed to assess both the physical and cognitive abilities of the suspect, providing crucial evidence in DUI investigations.

Procedure for OLS Test

What are the standard field sobriety tests used by police in Florida?

The officer will instruct the suspect to stand with one foot approximately six inches off the ground and count aloud until told to stop. The officer observes the suspect for signs of impairment, such as swaying, using arms to balance, hopping, or putting the foot down. These indicators help the officer determine if the suspect’s BAC is above the legal limit.

What is the One-Leg Stand test? The One-Leg Stand test is a field sobriety test where a suspect must stand on one leg and count aloud to demonstrate balance and coordination.

Indicators of Impairment

The One-Leg Stand test includes several indicators that officers look for to determine impairment:

  • Swaying While Balancing: The suspect exhibits side-to-side or back-and-forth motion while trying to maintain the one-leg stand position.
  • Using Arms for Balance: The suspect moves their arms six or more inches from their side to maintain balance.
  • Hopping: The suspect hops on the standing foot to maintain balance.
  • Puts Foot Down: The suspect is unable to maintain the one-leg stand position and puts the raised foot down one or more times during the 30-second count.

These indicators are critical in assessing whether a suspect’s BAC is above the legal limit. For more on how officers might make mistakes during these tests, visit our page on common mistakes in field sobriety testing.

How accurate is the One-Leg Stand test? The One-Leg Stand test is 65% accurate in identifying individuals with a BAC above 0.10, according to NHTSA research.

Scientific Validation of the OLS Test

The One-Leg Stand test has been scientifically validated through extensive research conducted by the National Highway Traffic Safety Administration (NHTSA). Here’s a brief overview of the findings:

  • Initial Research: The Southern California Research Institute (SCRI) identified the OLS test as one of the most accurate field sobriety tests for distinguishing BACs above 0.10.
  • Accuracy: The OLS test alone is 65% accurate in identifying individuals with a BAC above 0.10.
  • Field Validation Studies: Subsequent field validation studies in Colorado, Florida, and San Diego confirmed the test’s reliability under real-world conditions.

These findings underscore the importance of the OLS test in DUI investigations. Its scientific basis provides a robust foundation for its use in the field. For more details on the accuracy of field sobriety tests, visit our page on the effectiveness of the One-Leg Stand test.

Challenging OLS Test Results

Despite its reliability, the OLS test is not infallible. Various factors can affect its accuracy, and understanding these can be crucial in challenging the test results:

  • Medical Conditions: Certain medical conditions, such as neurological disorders or injuries, can affect balance and coordination.
  • Environmental Factors: Uneven surfaces, poor lighting, or adverse weather conditions can interfere with the test’s administration.
  • Improper Administration: The test must be administered according to strict guidelines. Any deviation from the standard procedure can compromise the results.

Challenging the OLS test results requires a thorough understanding of these factors. An experienced DUI attorney can scrutinize the test’s administration and identify potential issues that may weaken the prosecution’s case. For more information on challenging field sobriety tests, visit our page on challenging the Walk-and-Turn test in DUI defense.

The results of the OLS test can have significant legal implications. If the test indicates impairment, it can provide probable cause for arrest and be used as evidence in court. However, the reliability of the test results can be contested on various grounds, including:

  • Officer Training: The officer administering the test must be properly trained and certified. Lack of proper training can be a basis for challenging the test results.
  • Documentation: Detailed documentation of the test’s administration and the suspect’s performance is crucial. Incomplete or inaccurate documentation can cast doubt on the test’s validity.
  • Expert Testimony: Expert witnesses can provide valuable insights into the test’s scientific basis and potential flaws. Their testimony can help challenge the prosecution’s evidence.

Understanding the legal implications of the OLS test results is essential for anyone facing DUI charges. For more insights into the legal challenges of field sobriety tests, explore our page on challenging HGN evidence.

The One-Leg Stand test is a critical component of DUI investigations in Florida. Its scientific basis and accuracy make it a valuable tool for law enforcement. However, understanding its limitations and potential challenges is crucial for a robust defense. For more information on the role of field sobriety tests in DUI cases, visit our page on the role of field sobriety tests in court cases.


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What are the most common field sobriety tests used by police in Florida?

The most common field sobriety tests used by police in Florida are the Horizontal Gaze Nystagmus (HGN) test, the Walk-and-Turn (WAT) test, and the One-Leg Stand (OLS) test. These tests are designed to assess a suspect’s balance, coordination, and eye movements to determine impairment.

How accurate are field sobriety tests in detecting impairment?

Field sobriety tests have varying levels of accuracy. The Horizontal Gaze Nystagmus (HGN) test is 77% accurate, the Walk-and-Turn (WAT) test is 68% accurate, and the One-Leg Stand (OLS) test is 65% accurate in identifying individuals with a BAC above 0.10. Combining HGN and WAT tests can achieve an 80% accuracy rate.

Can medical conditions affect the results of field sobriety tests?

Yes, medical conditions can affect the results of field sobriety tests. Conditions such as neurological disorders, injuries, and certain medications can impact balance, coordination, and eye movements, potentially leading to false positives in these tests.

What are the legal consequences of refusing a field sobriety test in Florida?

Refusing a field sobriety test in Florida can result in serious legal consequences. Under Florida’s implied consent law, refusal can lead to an automatic driver’s license suspension and can be used as evidence of guilt in court. It’s important to understand your rights and the potential consequences before making a decision.







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