This description of the Walk and Turn test posted by San Francisco DUI Lawyer.

The next point is for an losing balance while turning. This item can only be scored if the suspect removes both feet from the line while turning or does not take several small steps, and pivots in one movement as in an about face movement. This would have been contrary to the directions given. It is imperative that the officer has demonstrated and articulated this movement properly in order to be scored. It is important that the officer be conservative in their evaluation of this turn and not be overly critical. 

Finally, the last scoring factor is when the suspect takes the incorrect amount of steps. This item is scored only once, even if an incorrect amount of steps are taken in both directions. The suspect was instructed to look down at their feet while performing this stage of the test and to count their steps out loud. If they do not look down at their feet or do not count out loud they can not be scored a point as these are not one of the scoring factors.

An officer is trained to document these observations but not to score them as part of the test. 

There are two ways that the suspect can receive a maximum of eight points on this test. If they step off the line three or more times or they can not do the test. If they can not do the test, this must be explained by the officer. A degree of reliability has been attached to this test of 68 percent. If the suspect receives a minimum of two points on this test, the officer is trained to use this as probable cause to believe that the suspect is under the influence of an alcoholic beverage and to make an arrest.