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Divided Attention Testing

The walk-and-turn test and one-leg stand test are "divided attention" tests that are easily performed by most sober people. They require a suspect to listen to and follow instructions while performing simple physical movements. Impaired persons have difficulty with tasks requiring their attention to be divided between simple mental and physical exercises.

In the walk-and-turn test, the subject is directed to take nine steps, heel-to-toe, along a straight line. After taking the steps, the suspect must turn on one foot and return in the same manner in the opposite direction. The examiner looks for seven indicators of impairment: If the suspect-

Cannot keep balance while listening to the instructions
Begins before the instructions are finished
Stops while walking to regain balance
Does not touch heel-to-toe
Uses arms to balance
Loses balance while turning
Takes an incorrect number of steps

NHTSA research indicates that 68 percent of individuals who exhibit two or more indicators in the performance of the test will have a BAC of 0.10 or greater.

In the one-leg stand test, the suspect is instructed to stand with on foot approximately six inches off the ground and count aloud by thousands (One thousand-one, one thousand-two, etc.) until told to put the foot down. The officer times the subject for 30 seconds. The officer looks for four indicators of impairment, which are:

Swaying while balancing
Using arms to balance
Hopping to maintain balance
Putting the foot down

NHTSA research indicates that 65 percent of individuals who exhibit two or more such indicators in the performance of the test will have a BAC of 0.10 or greater.

The effectiveness of SFST in court testimony and evidence depends upon the cumulative total of impairment indicators provided by the three-test battery. The greater the number of indicators, the more convincing the testimony. Because SFST is administered according to national standards and is supported by significant research, it has greater credibility than mere subjective testimony.