Law enforcement uses Field Sobriety Tests (FSTs) as standard procedures to evaluate driver impairment. The Horizontal Gaze Nystagmus (HGN) and Walk-and-Turn and One-Leg Stand tests are meant to evaluate coordination, balance, and cognitive ability. However, they are far from foolproof. The judicial system permits challenges of evidence based on false positive results which stem from various medical causes and incorrect test administration practices.

Your defense against DUI charges based on field sobriety tests can be strengthened through proper knowledge of how to contest these results. The following list outlines important methods to dispute field sobriety tests and protect your legal rights.

1. Understand the Limitations of Field Sobriety Tests

The initial step for building effective defenses against field tests involves recognizing their main weaknesses. Field sobriety tests do not provide conclusive scientific proof of impairment in drivers. While law enforcement officers use them to establish probable cause for DUI arrests, research shows that their subjective nature leads to numerous errors.

Some key limitations include:

• Subjective officer interpretation: The outcome of tests depends on an officer's subjective evaluation that may include both individual prejudices and mistakes.
• Inaccuracy rates: Even under standardized test conditions, FSTs demonstrate inaccurate impairment detection in a significant percentage of cases.
• External factors: The ability of drivers to operate their vehicles can be affected by weather conditions, unpredictable road situations, and environmental distractions even when they are not under the influence of alcohol.

2. Identify Police Errors in Administering the Test

One of the strongest ways to challenge a field sobriety test is by proving that the officer did not administer the test correctly. Any deviation from the National Highway Traffic Safety Administration (NHTSA) field sobriety test procedures makes the results unreliable according to their strict guidelines.

Common police errors include:

• Improper instructions: Your ability to perform the test could have been negatively influenced if the officer provided insufficient test instructions or refused to answer your questions.
• Non-standardized tests: The court will not accept results from non-standardized sobriety tests, which include counting backward or touching your finger to your nose.
• Failure to account for environmental conditions: The performance of field sobriety tests becomes compromised when drivers have to deal with slippery road conditions, uneven pavement, or traffic noises.
• Lack of medical screening: Officers should inquire about medical situations affecting balance and coordination abilities before administering the test.

Your attorney can use improper field sobriety test procedures to make a case for discarding unreliable results.

3. Highlight Medical Conditions That Affect Performance

A sober person might fail a field sobriety test because of various medical conditions or physical impairments. Any of these health conditions can result in subpar field sobriety test results:

• Neurological conditions (e.g., multiple sclerosis, Parkinson’s disease) that impact balance and coordination.
• Inner ear disorders that affect equilibrium.
• Vertigo or dizziness that makes standing on one foot difficult.
• Injuries (e.g., knee, ankle, or back problems) that impair mobility.
• Anxiety or nervousness, which can lead to physical trembling or difficulty following instructions.

Your defense attorney can secure medical documentation and expert statements to demonstrate your deficient performance stemmed from medical disabilities rather than intoxication.

4. Challenge Environmental Factors That Affected the Test

Field sobriety tests usually occur on the roadside despite the uncontrolled nature of the environment. The following outside elements can produce negative effects on test execution:

• Uneven or slippery roads that make it hard to balance.
• Poor lighting that makes it difficult to see the officer’s instructions.
• Bad weather (rain, wind, or cold) that affects stability and concentration.
• Traffic and noise distractions that interfere with following directions.

By demonstrating video evidence, witness statements, or expert assessments, your attorney can prove that testing conditions were unfavorable and affected the accuracy of results.

5. Question the Officer’s Experience and Training

Not all police officers receive the same training regarding field sobriety test administration. The results become unreliable when the officer does not possess sufficient training or experience.

Your attorney may investigate:

• The officer’s training record: An improper SFST training for the officer provides grounds to question their test results.
• Inconsistent testimony: Police reports that differ from video evidence can create uncertainty regarding police observation accuracy.
• Lack of documentation: Poor documentation of test results by the officer will reduce the strength of the prosecution's evidence against the defendant.

Your attorney can undermine the validity of the field sobriety test by questioning the arresting officer to reveal problematic execution or unreliable outcomes.

6. Use Video Evidence to Dispute the Officer’s Observations

Most DUI traffic stops are recorded using police dashcam technology and bodycam systems. The video evidence acts as essential proof when disputing field sobriety test results.

Video footage may show:

• The driver exhibited better performance than the officer reported in the documentation.
• External factors that potentially affected the accuracy of the performed test.
• Problems with the way the officer executed the test or gave instructions.

Video evidence can help disprove the officer's statements, weaken their credibility, and question the validity of FST results.

7. Challenge the Reliability of Standardized Field Sobriety Tests

Even when conducted correctly, standardized field sobriety tests (SFSTs) are not always reliable. Research has shown that even sober individuals can fail these tests due to nervousness, fatigue, or natural coordination issues.

Statistically, even under ideal conditions, the accuracy rates of standardized FSTs are:

• HGN Test – 77% accurate.
• Walk-and-Turn Test – 68% accurate.
• One-Leg Stand Test – 65% accurate.

Your attorney can present scientific studies and expert opinions to show that these tests fail to establish impairment as a fact.

Bottom Line

Field sobriety tests are a highly subjective method that frequently produces errors, making it one of the most disputed DUI evidence types. The results of field sobriety tests can be contested through various methods, including police mistakes, environmental factors, medical explanations, and evidence of improper testing procedures.

It is essential to seek advice from an experienced attorney when your arrest for DUI was based on a failed field sobriety test. They will be able to evaluate your arrest details and question the evidence to establish an effective defense.