This description of the One Leg Stand test posted by California DUI Lawyer.

In the Balance and Counting Stage, the officer instructs the suspect to raise one leg, either leg, approximately six inches off the ground, toes pointed out. This is demonstrated by the officer. The suspect is instructed to keep both legs straight, and his arms at his side. While they are keeping that position, they must count out loud for thirty seconds, one thousand one, one thousand two, etc., until told to stop. The count is demonstrated by the officer. They are then told to keep their arms at their side at all times, and watch their raised foot throughout the entire test. The suspect must again acknowledge that they understand the instruction to retain validity of the test. The person now is told to begin the test, while the officer must always time the 30 seconds. The test cannot be allowed to exceed thirty seconds. It must be terminated by the officer when thirty seconds expire. 

A suspect may be scored points for the following reasons. The suspect sways while balancing. The officer is trained not to be too critical in this scoring this. The suspect is a living, breathing person, and some sway will be noticed absent impairment. In order to score this point, swaying should be marked, such as a back-and-forth motion while the suspect maintains the one-leg-stand position.