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How We Challenge HGN Evidence and Win in 99% of Our DUI Cases




Understanding Horizontal Gaze Nystagmus (HGN) in DUI Cases

The Horizontal Gaze Nystagmus (HGN) test is a critical component of DUI investigations. This field sobriety test is designed to detect involuntary eye movements, or nystagmus, which can be indicative of alcohol impairment. However, the reliability and admissibility of HGN evidence are often contested in court.

What is Horizontal Gaze Nystagmus?

Horizontal Gaze Nystagmus refers to the involuntary jerking of the eyes as they gaze to the side. This phenomenon can be caused by various factors, not just alcohol consumption. During the HGN test, an officer will move a stimulus, such as a pen or finger, horizontally in front of the suspect’s eyes to observe these movements.

What is Horizontal Gaze Nystagmus? Horizontal Gaze Nystagmus is an involuntary jerking of the eyes as they gaze toward the side, often used in DUI investigations to detect alcohol impairment.

In a DUI investigation, the HGN test is typically the first field sobriety exercise performed. The officer will move the stimulus in at least 14 passes in front of the subject’s eyes. It’s important to note that many factors can cause nystagmus, not just alcohol consumption. For example, certain medical conditions, fatigue, and even prescription medications can lead to nystagmus.

During the HGN test, the officer will give specific instructions to the suspect:

  • Remove glasses: If the suspect is wearing glasses, they will be asked to remove them.
  • Keep head still: The suspect must keep their head still and follow the stimulus with their eyes only.
  • Follow instructions: The suspect is asked to follow the stimulus with their eyes without moving their head.

Understanding these instructions is crucial for the suspect, as any deviation can be interpreted as a sign of impairment. However, the administration of the HGN test is not infallible. According to the National Highway Traffic Safety Administration (NHTSA), the test must be conducted under strict guidelines to ensure its accuracy and reliability.

In Florida, the admissibility of HGN evidence in court is often challenged. For instance, in State v. Labrecque, the court found a lack of probable cause for DUI partly because the officer was not qualified to administer the HGN test. Similarly, in Dep’t of Highway Safety and Motor Vehicles v. Rose, the court ruled that HGN evidence should not have been considered at the Department of Highway Safety and Motor Vehicles (DHSMV) hearing.

Given these complexities, it’s essential for your DUI defense attorney to be well-versed in the NHTSA guidelines and the legal precedents surrounding HGN evidence. This knowledge can be pivotal in challenging the admissibility of HGN evidence and potentially getting it excluded from your case.

For more detailed information on field sobriety exercises, including the HGN test, you can refer to our Ultimate Guide to Field Sobriety Exercises in Florida. Understanding the nuances of these tests can significantly impact the outcome of your DUI case.

Common Mistakes in Administering the HGN Test

Officer administering HGN test during DUI stop

One of the key strategies in challenging HGN evidence is identifying errors in the test’s administration. Many officers fail to follow the National Highway Traffic Safety Administration (NHTSA) guidelines, rendering the test results unreliable.

Typical Errors Made by Officers

Common mistakes include moving the stimulus too quickly or too slowly, holding it too close or too far from the suspect’s face, and not maintaining the stimulus at maximum deviation for the required time. Any of these errors can compromise the test’s validity.

What are common mistakes in administering the HGN test? Common mistakes include moving the stimulus too quickly or too slowly, holding it too close or too far from the suspect’s face, and not maintaining the stimulus at maximum deviation for the required time.

Moving the Stimulus Incorrectly

One of the most frequent errors involves the movement of the stimulus:

  • Too Quickly: If the officer moves the stimulus too quickly, it doesn’t give the eyes enough time to follow the object properly, leading to inaccurate observations.
  • Too Slowly: Conversely, moving the stimulus too slowly can cause the suspect’s eyes to focus too intently, which may mask the signs of nystagmus.

Incorrect Distance from the Face

The distance at which the stimulus is held is also crucial for accurate results:

  • Too Close: Holding the stimulus closer than 12 inches can strain the suspect’s eyes and produce false positives.
  • Too Far: Holding the stimulus more than 15 inches away can make it difficult for the suspect to focus, leading to unreliable results.

Improper Maximum Deviation

Another critical aspect is maintaining the stimulus at maximum deviation:

  • Not Long Enough: The stimulus should be held at maximum deviation for at least four seconds. Failing to do so can prevent the officer from accurately observing nystagmus.
  • Incorrect Angles: Looping or curving the stimulus in an upward, downward, or circular motion instead of a straight line can also affect the test’s accuracy.

These mistakes are not just minor technicalities; they can significantly impact the reliability of the HGN test results. According to one study, the HGN test was administered incorrectly in the field over 90 percent of the time. This statistic underscores the importance of scrutinizing the administration of the HGN test in any DUI case.

For example, in State v. Labrecque, the court found a lack of probable cause for DUI partly because the officer was not qualified to administer the HGN test. Similarly, in Dep’t of Highway Safety and Motor Vehicles v. Rose, the court ruled that HGN evidence should not have been considered at the Department of Highway Safety and Motor Vehicles (DHSMV) hearing.

Given these complexities, it’s essential for your DUI defense attorney to be well-versed in the NHTSA guidelines and the legal precedents surrounding HGN evidence. For more insights into common mistakes officers make during field sobriety tests, you can refer to our comprehensive guide on officer errors in field sobriety testing.

Understanding these errors can be pivotal in challenging the admissibility of HGN evidence and potentially getting it excluded from your case. This can significantly weaken the prosecution’s case and increase your chances of a favorable outcome. For a broader understanding of field sobriety exercises, including the HGN test, visit our Ultimate Guide to Field Sobriety Exercises in Florida.

In Florida, the admissibility of Horizontal Gaze Nystagmus (HGN) evidence is a contentious issue. Courts often require that the administering officer have specialized training, such as being a Drug Recognition Evaluator (DRE), to testify about HGN results. This is because the HGN test is considered scientific evidence, and its reliability hinges on proper administration and interpretation.

Motions to Exclude HGN Testimony

Defense attorneys can file motions to exclude HGN testimony on the grounds that it constitutes scientific evidence requiring a qualified expert witness. If the officer lacks the necessary qualifications, the testimony may be deemed inadmissible. For example, in State v. Labrecque, the court found a lack of probable cause for DUI partly because the officer was not qualified to administer the HGN test. Similarly, in Dep’t of Highway Safety and Motor Vehicles v. Rose, the court ruled that HGN evidence should not have been considered at the DHSMV hearing.

What are the legal grounds for excluding HGN testimony? HGN testimony can be excluded if the administering officer lacks the necessary qualifications, as it constitutes scientific evidence requiring a qualified expert witness.

Understanding these legal nuances is crucial for building a strong defense. For instance, in Willis v. Dep’t of Highway Safety and Motor Vehicles, the court found that HGN evidence should not have been considered due to the officer’s lack of proper training.

Challenging the Officer’s Qualifications

One effective strategy is to challenge the officer’s qualifications. If the officer is not a certified Drug Recognition Evaluator (DRE), their testimony about the HGN test can be questioned. Courts are very particular about this aspect, and any deviation from the required qualifications can lead to the exclusion of the HGN evidence.

  • Drug Recognition Evaluator (DRE): Officers must have specialized training to administer and interpret the HGN test correctly.
  • Medical Professional Training: In some cases, officers must have training by a medical professional to testify about HGN results.

For more information on how officer qualifications can impact DUI cases, refer to our guide on common mistakes officers make during field sobriety testing.

Scientific Basis and Reliability

The HGN test is based on scientific principles, and its reliability is often questioned in court. Defense attorneys can argue that the test is not reliable enough to be used as evidence. This argument can be supported by pointing out any deviations from the National Highway Traffic Safety Administration (NHTSA) guidelines during the test administration.

For instance, the junk science behind field sobriety exercises can be used to question the scientific validity of the HGN test. Courts take these arguments seriously, and they can significantly impact the admissibility of HGN evidence.

Case Law Supporting Exclusion

Several cases support the exclusion of HGN evidence when proper procedures are not followed. For example, in State v. Meador, the Florida Supreme Court explained why HGN testimony should be excluded from trial unless the traditional predicates of scientific evidence are satisfied. This case highlights the importance of adhering to scientific standards when administering the HGN test.

Other notable cases include:

  • State v. Labrecque: Lack of probable cause due to the officer’s lack of qualifications.
  • Dep’t of Highway Safety and Motor Vehicles v. Rose: HGN evidence should not have been considered at the DHSMV hearing.
  • Willis v. Dep’t of Highway Safety and Motor Vehicles: Similar ruling as in Rose, emphasizing the need for qualified officers.

For a more detailed understanding of how legal precedents can affect your DUI case, visit our Ultimate Guide to Field Sobriety Exercises in Florida.

By leveraging these legal challenges, our firm has successfully excluded HGN evidence in numerous DUI cases. This approach not only weakens the prosecution’s case but also increases the chances of a favorable outcome for our clients.


Strategies for Successfully Challenging HGN Evidence

Our firm has a proven track record of challenging HGN evidence and winning DUI cases. We meticulously examine every aspect of the HGN test administration and the officer’s qualifications to identify weaknesses in the prosecution’s case. This rigorous approach often leads to the exclusion of unreliable HGN evidence, significantly weakening the prosecution’s case and increasing the chances of a favorable outcome for our clients.

Expert Cross-Examination Techniques

We employ expert cross-examination techniques to question the officer’s training, the conditions under which the test was administered, and any deviations from NHTSA guidelines. By focusing on these aspects, we can effectively challenge the reliability of the HGN test results. For instance, we scrutinize whether the officer followed the proper NHTSA guidelines during the test administration.

What are expert cross-examination techniques? Expert cross-examination techniques involve questioning the officer’s training, the conditions under which the test was administered, and any deviations from NHTSA guidelines to challenge the reliability of the HGN test results.

Our attorneys are well-versed in identifying common mistakes made by officers during the HGN test. These mistakes can include:

  • Moving the stimulus too quickly or too slowly: This can affect the accuracy of the test results.
  • Improper distance: Holding the stimulus too close or too far from the suspect’s face can compromise the test’s validity.
  • Incorrect timing: Not maintaining the stimulus at maximum deviation for the required time can lead to unreliable results.

By highlighting these errors during cross-examination, we can cast doubt on the prosecution’s case. For more details on common errors, refer to our guide on officer mistakes during field sobriety testing.

We also leverage legal precedents to challenge the admissibility of HGN evidence. For example, in State v. Labrecque, the court found a lack of probable cause for DUI partly because the officer was not qualified to administer the HGN test. Similarly, in Dep’t of Highway Safety and Motor Vehicles v. Rose, the court ruled that HGN evidence should not have been considered at the DHSMV hearing.

These cases highlight the importance of proper officer qualifications and adherence to scientific standards. By citing these precedents, we can argue for the exclusion of HGN evidence in your case.

Utilizing Expert Witnesses

Expert witnesses play a crucial role in challenging HGN evidence. We work with medical professionals and forensic experts who can testify about the scientific limitations of the HGN test. Their testimony can be instrumental in demonstrating that the test results are not reliable enough to be used as evidence.

For instance, experts can explain how various medical conditions can affect the results of the HGN test. This can be particularly useful in cases where the suspect has a history of neurological issues or other health problems that could cause nystagmus. For more on this topic, see our article on how medical conditions affect field sobriety exercises.

Highlighting Junk Science

Another effective strategy is to highlight the junk science behind the HGN test. Courts are increasingly skeptical of field sobriety tests that do not meet rigorous scientific standards. By exposing the flaws in the test’s methodology, we can argue that the results should not be admissible in court.

For example, the junk science behind sobriety assessments can be used to question the validity of the HGN test. This approach has been successful in many cases, leading to the exclusion of unreliable evidence.

Case Studies and Success Stories

Our firm has successfully challenged HGN evidence in numerous DUI cases. In one notable case, we were able to get the HGN evidence excluded because the officer did not follow the proper procedures. This significantly weakened the prosecution’s case, leading to a favorable outcome for our client.

In another case, we utilized expert testimony to demonstrate that the suspect’s medical condition could have caused the nystagmus observed during the HGN test. This testimony was crucial in getting the evidence excluded and ultimately winning the case.

For more success stories and strategies, visit our Ultimate Guide to Field Sobriety Exercises in Florida.

Continuous Education and Training

Our attorneys are committed to continuous education and training in DUI defense strategies. We regularly attend seminars and workshops to stay updated on the latest developments in field sobriety testing and DUI law. This commitment to professional development ensures that we are always prepared to challenge HGN evidence effectively.

By staying at the forefront of DUI defense, we can provide our clients with the best possible representation. For more information on our approach, see our page on how we challenge HGN evidence.

In conclusion, challenging HGN evidence requires a thorough understanding of the test’s scientific basis, rigorous cross-examination techniques, and the use of expert witnesses. Our firm excels in these areas, giving us a significant advantage in DUI cases. If you are facing DUI charges, contact us to discuss how we can help you challenge the HGN evidence and achieve a favorable outcome.

How We Challenge HGN Evidence and Win in 99% of Our DUI Cases


Infographic depicting the words How We Challenge HGN Evidence and Win in 99% of Our DUI Cases


What is the Horizontal Gaze Nystagmus (HGN) test?

The Horizontal Gaze Nystagmus (HGN) test is a field sobriety test used by law enforcement to detect involuntary eye movements, or nystagmus, which can indicate alcohol impairment. During the test, an officer moves a stimulus, such as a pen or finger, horizontally in front of the suspect’s eyes to observe these movements.

How can medical conditions affect the results of the HGN test?

Medical conditions can significantly affect the results of the HGN test. Conditions such as neurological disorders, certain medications, and even fatigue can cause nystagmus, leading to false positives. It’s essential to consider these factors when challenging HGN evidence in a DUI case.

What are the common mistakes officers make when administering the HGN test?

Officers often make several common mistakes when administering the HGN test, including:

  • Moving the stimulus too quickly or too slowly: This can affect the accuracy of the test results.
  • Improper distance: Holding the stimulus too close or too far from the suspect’s face can compromise the test’s validity.
  • Incorrect timing: Not maintaining the stimulus at maximum deviation for the required time can lead to unreliable results.

Can HGN evidence be excluded from a DUI case?

Yes, HGN evidence can be excluded from a DUI case. Defense attorneys can file motions to exclude HGN testimony on the grounds that it constitutes scientific evidence requiring a qualified expert witness. If the officer administering the test lacks the necessary qualifications, the testimony may be deemed inadmissible.


Explore additional areas of practice to see how we can assist you further:

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Officer Mistakes in FSEs Junk Science Behind FSEs
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Refusing Field Sobriety Tests Expert Witnesses for FSEs
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Weather Conditions and FSEs Role of FSEs in DUI Cases
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