Introduction
The Standardized Field Sobriety Test (SFST) refers to a group of three tests used by law enforcement officers during a traffic stop to check whether a driver is impaired or not. SFST is composed of three tests; horizontal gaze nystagmus (HGN), the walk-and-turn (WAT), and the one-leg stand test (OLS). It is used to assess the balance, coordination, and the ability of a driver to shift his/her attention to more than one task. The SFST is admissible in court in numerous states because they are scientifically validated. This paper will discuss how SFST is involved in alcohol-related driving offenses.
The Horizontal Gaze Nystagmus (HGN) Test
According to NHTSA research, the HGN test is 77% accurate by itself (JUSTIA, N.d). The HGN refers to an involuntary “jerking” of the eyeball which occurs when the individual rotates his/her eyes at high peripheral angles. The jerking of the individual’s eyes becomes more exaggerated and occurs at lesser angles if the person is intoxicated. In the HGN test, the law enforcement officer observes the suspect’s eyes as the suspect follows a slowly moving object (pen or flashlight). The officer checks: “if the eye cannot follow the object smoothly, if jerking is distinct when the eye is at maximum deviation, if the angle of jerking onset is within 45 degrees” (Buddy, 2018). If the suspect exhibits two or more of the indicators mentioned above, then his/her alcohol blood content is 0.1 or more.
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Walk-and-Turn (WAT) Test
According to NHTSA research, the WAT test is 68% accurate by itself (JUSTIA, N.d). WAT involves taking nine steps, heel-to-toe, along a straight line. Once the suspect completes this, he/she turns on one foot and returns nine steps in the opposite direction. The law enforcement officer checks; whether the suspect is unable to keep balance while delivering the instructions, starts taking steps before final instructions, loses balance while walking and stops to regain it, fails to touch heel-to-toe, keeps balance using his/her arms, loses balance when turning, and takes less or more steps (Buddy, 2018). If the suspect exhibits two or more of the indicators mentioned above, then his/her alcohol blood content is 0.1 or more.
The One-Leg Stand (OLS) Test
According to NHTSA research, the OLS test is 65% accurate by itself (JUSTIA, N.d). In OLS, the suspect is asked by the officer to stand on one foot approximately six inches off the ground. The suspect is then asked to count from 1,001 upwards until he/she is asked to put down the foot (approximately after 30 seconds). The officer checks the following indicators: if the suspect sways while balancing, keeps balance using his arms, hops to keep balance, and fails to stand on one foot (Buddy, 2018). If the suspect exhibits two or more of the indicators mentioned above, then his/her alcohol blood content is 0.1 or more.
References
Buddy, T. (2018). Field Sobriety Test to Assess Drunk Driving. [Online]. Available at: https://www.verywellmind.com/field-sobriety-test-67159 . Accessed 1 st March 2019.
JUSTIA. (N.d). Concepts and Principles of the Standardized Field Sobriety Tests. [Online]. Available at: https://www.justia.com/criminal/drunk-driving-dui-dwi/docs/standardized-field-sobriety-tests/ . Accessed 1 st March 2019.
