A field sobriety test (FST) is a series of physical and cognitive tests conducted by law enforcement officers to determine if a driver is impaired by alcohol or drugs while operating a vehicle. These tests are typically administered during a traffic stop if the officer suspects the driver of driving while intoxicated (DWI) or driving under the influence (DUI). It's important to note that specific laws and procedures may vary by jurisdiction, so it's always advisable to consult the laws in your specific area for accurate information.


Commonly used field sobriety tests include:


Horizontal Gaze Nystagmus (HGN) Test


The officer observes the driver's eyes as they track a stimulus, usually a pen or small flashlight, moving horizontally. Nystagmus, an involuntary jerking of the eyes, can be more pronounced when a person is impaired.


Walk-and-Turn Test


The driver is asked to take a series of steps in a straight line, heel-to-toe, then turn around and return in the same manner. The officer looks for specific indicators of impairment, such as losing balance, stepping off the line, or not following instructions.


One-Leg Stand Test


The driver is instructed to stand with one foot raised approximately six inches off the ground while counting out loud. The officer watches for signs of impairment, such as swaying, using arms for balance, or putting the foot down.


These tests are designed to assess a driver's divided attention, balance, coordination, and ability to follow instructions. They are not foolproof, and other factors like physical conditions, nervousness, or fatigue can affect performance. However, if the officer observes signs of impairment during these tests, they may provide probable cause for the officer to proceed with further testing, such as a breathalyzer test or blood test to measure blood alcohol concentration (BAC).


It's important to cooperate with law enforcement officers during a traffic stop, but you also have rights. If you are arrested for DWI based on the results of a field sobriety test, it is advisable to consult with a lawyer who can provide legal advice based on the specific laws and regulations in your jurisdiction.



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