Tests sponsored by the National Highway Traffic Safety Administration revealed that the HGN test is most reliable (77 percent), followed by the walk-and-turn test (68 percent) and the one-leg-stand test (65 percent). The three tests should be used in combination to ensure maximum accuracy in determining probable cause for a drunk driving arrest. The HGN test involves the officer's moving an object before the suspect's eyes to determine the degree to which the suspect's eyes can smoothly follow the object, to assess jerkiness of the eyes when held at maximum side deviation, and to determine the point at which eye jerking begins. The walk-and-turn test involves nine heel-to-toe steps along a straight line, turn on the line, and a nine-step return. The test gauges the suspect's ability to perform a simple physical task and follow verbal instructions. The one-leg stand tests the suspect's ability to balance, listen to instructions, and count aloud. The pamphlet instructs officers in how to conduct and interpret each test, the limitations of field sobriety tests, and establishing probable cause to arrest. Discussion guide, questions and answers on the material, and 1 reading suggestion.