Correct administration and scoring of the walk and turn field test requires certain factors. It must be performed on a hard, dry, level, non-slip surface. There must be sufficient room for the suspect to complete nine heel-to-toe steps. This test loses some validity when conducted in certain wind or weather conditions. This happens if the weather prevents the standards of administration from being met. The manual calls for a straight line. It must be clearly visible on the surface, but the test can be performed parallel to the curb. Conditions must also be such that the suspect would be in no danger if they were to fall.
Some people should not be given this test because even the average sober person would have difficulty with it. People more than sixty five years of age or over fifty pounds overweight or with any physical impairment should not be given this test. The officer is trained to take this into account when developing their probable cause for arrest. Individuals wearing heels more than two inches high should be able to remove their shoes. These shoes may affect the subject’s ability to balance and hinder the validity of the results. Individuals who can not see out of one eye may also have trouble with this test. This is because of poor depth perception. They should not be given this test as well.
About the Test
The walk and turn field test is an objective test. It is based upon certain predictable errors that a person under the influence will display. There are also scoring factors that will give the officer a basis for passing and failing other than a subjective opinion. In order to properly administer this test, it is important to understand what type of test this is. It is commonly referred to as a divided attention test. This is because it divides the suspect’s attention between mental and physical tasks. The physical tasks include balance and coordination. The mental tasks include comprehension of verbal instructions, the processing of information and the recall of memory. While a person may be able to perform one task, they may not be able to perform the other if under the influence of alcohol.
Administering the Test
While the suspect is performing this test, the officer must observe the suspect from three or four feet away. The officer should remain motionless. Being too close or creating a distraction with excessive motion may cause the suspect to make errors they may not have committed otherwise. This will cause some validity of the results to be lost. Even a sober person may have difficulty under these particular conditions. The officer must give clear verbal instructions, only to supplement this with a demonstration of the test, and must receive affirmative confirmation of the suspect’s comprehension of the instructions.
The walk and turn field test is scored in relation to eight scoring factors that can be seen in two separate stages. When administered alone, the walk and turn test is considered to be 68% accurate, however, when combined with the horizontal gaze nystagmus, the two are considered to be 80% accurate in detecting impaired drivers.
The first stage of this test is called the instruction stage and will set the stage for the entire test. If the officer does not follow training and procedure perfectly during this stage, it may affect the validity of the entire test. The officer must verbally explain to the suspect the heel to toe stance and then demonstrate it. The suspect is told to place their left foot on the line. They have to place their right foot on the line ahead of the left foot. They do this with heel of right foot against toe of left foot. In the absence of a demonstration, instructions alone can discredit the validity of the test.
The officer is instructed by way of training to make sure the right foot is in front of the left foot to start in order to maintain uniformity. This also becomes important later in the test during the turning evaluation. If the suspect is instructed or demonstrated improperly, it may affect the suspect during this part of the test. After accomplishing the starting position, the officer must inform the suspect to remain in that position until they are told to start walking.
There are two ways that the officer can assess a point against the suspect’s performance. If the suspect cannot keep balance while listening to the instructions, a point is scored. This item is only scored if the suspect does not maintain the heel to toe position throughout the instructions. The officer is trained to be conservative in their scoring and not to score a point if the suspect sways or uses the arms to balance but maintains the starting position during this stage.
A second scoring factor is known as starting too soon. This is given when the starts to walk before the officer instructs them to do so. This can only be scored if the officer specifically instructed the suspect not to start until told to begin and the suspect stated they understood this instruction.
The second stage of this test is known as the walking stage. The suspect is informed again, that when told to start, they must take nine heel to toe steps, turn around, and take nine heel to toe steps back. The officer must demonstrate two or three heel to toe steps for the suspect, as well as how to turn: the foot must be kept on the line and turn by taking a series of small steps. The officer then continues to instruct the suspect to keep their arms at their sides while walking. They have to watch their feet at all times, to count their steps aloud and not to stop once they have begun.
If the officer does not once again confirm the suspect’s understanding of the instructions, the test results may be invalid.