Standardized Field Sobriety Testing (SFSTs)

Standardized Field Sobriety Tests (SFSTs) were developed in the 1970s by the National Highway Traffic Safety Administration (NHTSA) in partnership with the International Association of Chiefs of Police (IACP) and the National Sheriffs' Association (NSA).

The SFSTs were created as a way to standardize the field sobriety testing process and improve the ability of law enforcement officers to determine if a driver is impaired by alcohol or drugs. Prior to the development of the SFSTs, officers used a variety of different tests to make this determination, and there was no consistency in how the tests were administered or evaluated.

The Standardized Field Sobriety Tests (SFSTs) are a series of tests used by law enforcement officers to determine if a driver is impaired by alcohol or drugs. The SFST battery is made up of three tests: the horizontal gaze nystagmus (HGN) test, the walk-and-turn test, and the one-leg-stand test.

The Horizontal Gaze Nystagmus (HGN) Test: This test is used to measure the involuntary jerking of the eye that occurs when a person is under the influence of alcohol. The officer will ask the driver to follow a small object, such as a pen or a flashlight, with their eyes as it is moved horizontally. The officer will look for three clues of impairment: if the eye cannot follow a moving object smoothly, if the eye jerks at a certain angle, and if there is a distinct jerking of the eye as it is held at maximum deviation.

The Walk-and-Turn Test: This test is used to measure a person's ability to divide their attention and follow instructions. The officer will ask the driver to take nine heel-to-toe steps in a straight line, turn around, and take nine heel-to-toe steps back. The officer will look for eight clues of impairment: if the driver loses balance during the instruction phase, if they start too soon, if they stop while walking, if they do not walk heel-to-toe, if they step off the line, if they use their arms to balance, if they turn improperly or if they take an incorrect number of steps.

The One-Leg-Stand Test: This test is also used to measure a person's ability to divide their attention and follow instructions. The officer will ask the driver to stand on one foot and raise the other foot six inches off the ground, keeping their arms at their sides. The officer will ask the driver to count out loud, one thousand one, one thousand two, etc. The officer will look for four clues of impairment: if the driver sways while balancing, if they use their arms to balance, if they hop or if they put their foot down.

Non-Standardized Field Sobriety Testing

In addition to the Standardized Field Sobriety Tests (SFSTs), law enforcement officers may use a variety of non-standardized tests to detect impairment caused by alcohol or drugs. These tests are not part of the official SFST battery and may not have been validated through research.

The Alphabet Test: This test is used to measure a person's ability to follow simple instructions and their cognitive function. The officer will ask the driver to recite the alphabet, either forwards or backwards, starting at a certain letter. The officer will look for slurred speech, an inability to complete the task, or an inability to start the task.

The Finger-to-Nose Test: This test is used to measure a person's motor skills and coordination. The officer will ask the driver to touch the tip of their nose with their index finger, with their eyes closed or open. The officer will look for an inability to touch the nose, or an inability to touch the nose accurately.

The Finger Count Test: This test is used to measure a person's cognitive function and ability to follow instructions. The officer will ask the driver to hold up a certain number of fingers and then count them. The officer will look for an inability to hold up the correct number of fingers, or an inability to count the fingers accurately.

The Rhomberg Balance Test: This test is used to measure a person's ability to balance and their sense of time. The officer will ask the driver to stand with their feet together, eyes closed, and head tilted back. The officer will ask the driver to estimate when 30 seconds have passed. The officer will look for an inability to maintain balance, or an inability to estimate the time accurately.