Field sobriety test analyzer

Legal information only. FST analysis requires review of the actual police report and dash cam footage. This analyzer identifies potential issues for your attorney to investigate. See our full disclaimer.

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FST protocol violations identified in the police report and dash cam footage can make the test results inadmissible or significantly undermine their value. Free DUI case review.

Why do NHTSA protocols matter so much in DUI cases?

The 3 standardized field sobriety tests were developed and validated by the National Highway Traffic Safety Administration through controlled research studies. The HGN test correctly identifies impaired drivers in 88% of cases, the walk-and-turn in 79%, and the one-leg-stand in 83% - but only when administered exactly according to the standardized procedures. Any deviation from protocol reduces that accuracy, potentially to the point of being scientifically unreliable.

Defense attorneys and prosecutors both know this. An officer who conducted FSTs on a gravel shoulder with passing traffic lights, failed to give proper instructions, and administered the walk-and-turn on a visible slope has not conducted NHTSA-standardized tests - they've conducted their own informal physical coordination tests with no validated accuracy rate. Courts regularly exclude or limit FST evidence based on administration deficiencies. Combine your FST issues with the BAC timeline analysis and the breathalyzer accuracy evaluation for a comprehensive defense package to present to your attorney.

What medical conditions affect FST performance?

NHTSA itself acknowledges that field sobriety tests have reduced reliability for certain populations: people 65 years or older, people 50 or more pounds overweight, and people with inner ear disorders, back problems, knee injuries, ankle problems, or neurological conditions. Officers are supposed to inquire about medical conditions before administering FSTs and note any disclosed conditions in their report. When an officer fails to ask about medical conditions or ignores disclosed conditions, the resulting FST performance is attributable to the medical condition rather than alcohol impairment.

Is dash cam footage of FSTs important?

It is often the most important piece of evidence in a DUI FST challenge. The officer's report describes the FSTs from their perspective - unsurprisingly, they rarely note their own protocol violations. The dash cam video shows the actual conditions: the surface slope, the lighting, whether the stimulus was held at the correct distance, whether the officer interrupted the test, and how the defendant actually performed versus how the officer described the performance. A DUI attorney requests the dash cam footage immediately after arrest because police body camera and dash cam footage is sometimes deleted after 30 to 90 days if not preserved.

Frequently asked questions about field sobriety tests

In most states, field sobriety tests are voluntary. You can politely decline without triggering automatic license suspension (unlike chemical breath test refusal under implied consent laws). However, refusing FSTs may still be noted by the officer and mentioned at trial as evidence of consciousness of guilt. The practical calculation is: if you've had nothing to drink or very little, FSTs may help you. If you've had several drinks, FSTs are more likely to hurt than help. An attorney can advise on the refusal strategy before you are ever stopped - knowing your rights in advance is better than deciding in the moment.

The Horizontal Gaze Nystagmus test measures the involuntary jerking of the eyes that occurs when they track a moving stimulus. Alcohol causes nystagmus to begin at a smaller angle of gaze, become more pronounced, and appear at maximum deviation. The officer moves a stimulus (pen, finger, or light) horizontally while looking for 6 clues: lack of smooth pursuit in each eye, distinct nystagmus at maximum deviation in each eye, and onset before 45 degrees in each eye. Four or more clues suggest BAC above 0.08% in the original NHTSA validation studies - under standardized conditions that are frequently not met in the field.

Yes, significantly. Being pulled over by police at night, standing on a highway shoulder with passing traffic, and being watched carefully while performing physical tasks is an anxiety-inducing situation for virtually anyone. Anxiety affects balance, coordination, and the ability to follow multi-step instructions under pressure. These are exactly the things FSTs measure - and anxiety produces the same observable signs as alcohol impairment: unsteady balance, difficulty with divided attention tasks, and stress-related physiological responses. Defense attorneys make this argument effectively, particularly when other evidence of impairment is weak.

According to NHTSA, 2 or more clues on the walk-and-turn test indicate a BAC above 0.08% in approximately 79% of cases under standardized conditions. The 8 clues are: cannot keep balance during instructions, starts before instructions finished, stops while walking, misses heel-to-toe, steps off the line, uses arms for balance, improper turn, and wrong number of steps. The 79% accuracy figure - meaning 21% of people with 2+ clues are actually below 0.08% - is itself a significant foundation for reasonable doubt when FSTs are the primary evidence.

Non-standardized field sobriety tests like reciting the alphabet, counting backward, or touching your nose have no NHTSA validation research behind them. Their accuracy at identifying impairment is unknown. Courts admit them as observations of coordination and divided attention but their evidentiary value is significantly lower than standardized tests - and a DUI attorney challenges their validity in front of a jury by pointing out the absence of scientific validation. Officers sometimes administer non-standardized tests when they have doubts about the strength of their standardized test observations.