Massachusetts police officers are trained to administer a series of tests to evaluate whether drivers are impaired. These Standardized Field Sobriety Tests (SFST’s) were designed to be successfully performed by the average sober person, and are said to test the mental and physical capabilities needed to safely operate a motor vehicle. More specifically, FST’s allow police officers to evaluate a driver’s balance, information processing, short-term memory, vision, small muscle control, and coordination.
Proper administration of FST’s tests a driver’s divided attention that requires concentration in one area while performing another task. After studies by the National Highway Traffic Safety Administration, three tests were found to reliably distinguish drivers having blood alcohol content (BAC) above 0.10%. Those tests are: (1) Horizontal Gaze Nystagmus, (2) 9-Step Walk and Turn, and (3) the One-Leg Stand.
Other tests often used by police officers, including recitation of the alphabet, thumb-to-finger touch test, and touching of nose have not been scientifically validated.
There are three (3) Standardized Field Sobriety Tests. Each is a "divided attention test" designed to challenge mental and physical simultaneously. Factors such as a recent collision, injuries, age, weight, weather, footwear, and ADHD can affect performance on SFSTs. Incorrect instructions by officers can lead to confusion, mistakes, and misinterpreted results.
The HGN Test examines a person's eye movement. Movement of the eye is directed by six muscles controlled by the central nervous system (CNS). Nystagmus is an involuntary movement of the eye that becomes visible when the CNS is affected. The CNS can be affected by a variety of factors; one factor is the consumption of alcohol. Alcohol slows the muscular control of the eyes, causing eye movement to appear as “jerking” and lacking smooth back-and-forth movement.
The WAT Test is sometimes known to most lay people as “walking the line.” The Walk and Turn test is administered, and graded, in two stages: the Instruction Stage and Walking Stage.
Instruction Stage: The officer explains the test. This is a graded portion of the test, where an inability to keep balance or raising arms to maintain balance.
Walking Stage: During the Walking Stage, the driver takes nine steps forward in a straight line, touching heel to toe, turns, and repeats.
The One Leg Stand Test is administered and graded in two stages: an Instruction Stage and Balance & Counting Stage.
Instruction Stage: The officer explains the test while looking for clues, such as swaying while balancing.
Balance & Counting Stage: The driver is required to stand on one foot, raise the other foot approximately six (6) inches off the ground, with toes pointed forward for 30 seconds. Both legs must be straight and arms down to the side. Ihe driver must count out loud while keeping
These tests are not “standardized” and have no statistical or scientific basis. They are often applied inconsistently. These tests are used to make additional observations that suggest impairment and stack circumstantial evidence.
The officer requires the driver to recite the alphabet, from the letter “A” to “Z,” without singing the “alphabet song” most of people learned as children. Some officers add a twist to make this test more difficult by having drivers start and end at other letter, for instance, reciting the alphabet from the letter “C” to the letter “Q.” Clues the police look for include slurred speech, missing letters, mixing the order of letters, and starting or stopping at the wrong letter.
The officer randomly selects two numbers for the driver to count backwards from, for instance, 89 to 52. Counting backwards requires more cognitive capability than counting forward, and having the driver remember which numbers to start and end at make the task for difficult.
Also known as the Finger Count, the driver is required to touch the tip of his thumb to the tip of each finger while simultaneously counting upwards, one (1) through four (4), then in reverse order four through one. Most officers require a driver to complete this task three times, and are looking to see if the person becomes confused in the numbering sequence or has difficulty touching thumb to fingertip.
The driver is instructed to stand with feet together, head back, eyes closed, with both arms extended and index fingers pointing outward. When the officer calls out “Right” or “Left” the driver is required to touch the tip of that hand’s index finger to the tip of the nose. The officer may call out any variation of “right” or “left” while looking to see if the person has difficulty with balance or touching the tip of the nose.
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