Often misunderstood field sobriety testing is used by police officers to establish probable clause to arrest a potential suspect for driving while intoxicated to administer a breathalyzer to determine whether a per se violation (.08 BAC ) has occurred. However, field sobriety testing can also be used to convict an individual of driving while intoxicated without the establishment of a per se violation. Thus, the examination and understanding of field sobriety testing is of paramount importance because the defendant must not only defeat the breath test result but also the officers subjective interpretation of the field sobriety tests.
Psychophysical tests should require not only the evaluation of a person’s appearance and condition but also their ability to follow instructions, balance, and coordination. Generally, tests require the individual to concentrate on more than one thing at a time thus dividing their attention between mental and physical tasks. The reason this is done is because scientific studies have shown that individuals under the influence generally cannot perform both tasks simultaneously.

Certain tests have been approved by the National Highway Traffic Safety Administration (NHTSA) for use in establishing whether an individual has been driving while intoxicated. These tests are the Horizontal Gaze Nystagmus (HGN), the walk and turn, and one leg stand. There are no other approved tests by the National Highway Traffic Safety Administration including reciting the alphabet, touching your nose, or any sway test. Additionally, the approved tests must be given by trained individuals as taught. Failure to properly administrate the tests should invalidate their use as their scientific reliability will be impaired.

The HGN is performed using a penlight or pen. The officer has the individual follow the movement of the pen without turning their head. The purpose is to watch the eyes to determine when involuntary jerking of the eye begins. The officer initially checks for smooth pursuit of the eye. Score factors are given and if enough scoring factors are accumulated, the individual is deemed to fail the test. While an individual must be allowed to uses eyeglasses during the test hard contacts must be removed. The test is generally performed several times to clearly establish the point factor. Officers in New Jersey are required to keep a log of all HGN performed and cannot rely on the test until they have performed ten field tests.

The walk and turn test is required to be performed on a hard, dry, level, non-slippery surface, preferably with a straight line clearly marked on the ground and sufficient room for the individual to perform at least nine heel-to-toe steps. Weather conditions including wind, rain, and snow can affect the validity of the test as can non-level surfaces, slippery surfaces, improper lighting, flashing lights, absence of a straight line, a person’s physical condition, persons weight, and the type of shoe worn. People over the age 65, more than 50 pounds overweight, and those with physical impairments which affect balance should not be given this test. Individuals wearing heels higher than two inches should be required to remove their shoes prior to taking the test. Individuals with depth perception problems also should not be given this test.

The officer is required to give clear verbal instructions and properly demonstrate what is required. It is imperative that the officer make sure the individual understands the instructions completely prior to engaging the individual to begin the test. The actual first part of the test is the individual’s ability to understand and follow the instructions as given. The officer must give the individual clear instructions to place the left foot on the line with the heel of the right foot against the toe of the left. The officer scores points for the individual’s ability to follow the instructions and maintain their balance while listening to the instructions and to maintain their balance at the beginning of the test.

The individual is then instructed to take nine steps forward placing each foot heel- to-toe. The officer having previously demonstrated the procedure. The officer also will demonstrate and inform the individual on the required method for turning. Generally, the turn consists of the individual keeping one foot on the line and taking several small steps to complete the turn. During this phase of the test the individual is instructed to keep their arms at their side and not to stop once they start walking. The officer will assess points for failing to walk heel-to-toe, stepping off the line, taking incorrect number of steps either forward or back, making an improper turn, stopping, or raising the arms.

The one leg stand must be performed on a hard, dry, level, non slippery surface. Proper lighting is required as absence of proper lighting deprives the individual of a visual frame of reference making this test similar to a sway test. The officer must clearly explain the instructions to the individual and demonstrate the procedure. Factors as listed for the walk and turn test must be considered for the one leg stand in determining which individuals can be given this test. There are two separate parts to this test. The first part is the instruction phase. The second part is the performance phase.

During the instruction phase the officer advises the individual to stand with heels together and arms at their sides. The individual is instructed not to begin the test until told. The performance phase consists of balance and counting. The individual is instructed to stand on either foot as preferred and raise the other foot approximately six inches off the ground. The individual is instructed to maintain this position and count out loud for 30 seconds by one thousands. The individual is allowed to look at his foot while counting but must maintain his arms at his sides. The individual is also instructed not to hop or sway. Points can be assessed for swaying, using arms for balance, touching their foot to the ground, or hopping.

The actual testing and training are more detailed than this summary of the tests. However these are the approved tests as outlined by the NHTSA and are the only tests which the officer should rely in determining whether to arrest in individual for purposes of a breathalyzer test and are the only tests for which the court should rely in determining whether an individual has been operating a vehicle while intoxicated.