PAS - ALCO SENSOR IV The most important thing to know about FST's is that when performed correctly - which is rare - are only 79% accurate in the determination of whether someone is under the influence! This is just barely a passing grade. They are aimed at assisting the officer in deciding whether the person should be arrested or not. The value for conviction is entirely a different story.

When a driver is pulled over on a routine drunk driving stop and the police officer suspects intoxication, field sobriety tests may be conducted. The driver must perform simple physical or cognitive tests to determine sobriety. The National Highway Traffic and Safety Administration (NHTSA) guidelines were set up to help make these tests more accurate. They are now called ‘standardized field sobriety tests.’You can learn extensive knowledge about this specific test by contacting our office.


  • the one-leg stand
  • walk and turn
  • horizontal gaze nystagmus test

The proper way to administer them is as follows:

HGN Testing

Horizontal Gaze Nystagmus is an involuntary jerking of the eye that occurs naturally as the eyes gaze to the side. Under normal circumstances, nystagmus occurs when the eyes are rotated at high peripheral angles. However, when a person is impaired by alcohol, nystagmus is exaggerated and may occur at lesser angles. An alcohol-impaired person will also often have difficulty smoothly tracking a moving object. In the HGN test, the officer observes the eyes of a suspect as the suspect follows a slowly moving object such as a pen or small flashlight, horizontally with his or her eyes. The examiner looks for three indicators of impairment in each eye: if the eye cannot follow a moving object smoothly, if jerking is distinct when the eye is at maximum deviation, and if the angle of onset of jerking is within 45 degrees of center. If, between the two eyes, four or more clues appear, the suspect likely has a BAC of 0.08 or greater. NHTSA research found that this test allows proper classification of approximately 88 percent of suspects (Stuster and Burns, 1998). HGN may also indicate consumption of seizure medications, phencyclidine, a variety of inhalants, barbiturates, and other depressants.

Walk and Turn

The Walk-and-Turn test and One-Leg Stand test are "divided attention" tests that are easily performed by most unimpaired 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 eight 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, steps off the line, uses arms to balance, makes an improper turn, or takes an incorrect number of steps. NHTSA research indicates that 79 percent of individuals who exhibit two or more indicators in the performance of the test will have a BAC of 0.08 or greater (Stuster and Burns, 1998).

One Leg Stand

In the One-Leg Stand test, the suspect is instructed to stand with one 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, including swaying while balancing, using arms to balance, hopping to maintain balance, and putting the foot down. NHTSA research indicates that 83 percent of individuals who exhibit two or more such indicators in the performance of the test will have a BAC of 0.08 of greater (Stuster and Burns, 1998).

Officers may, however, also administer non-standardized tests, which might include:

  • stand with feet together and tip the head backwards
  • count the number of fingers that the officer raises
  • recite the alphabet or a portion of it
  • count backwards
  • Rhomberg stationary balance test: the driver stands, feet together, and leans the head back to look up at the sky while holding their arms out to the side
  • finger-to-nose: this requires the driver might to close his or her eyes and bring the finger around to touch the nose
  • hand-pat test: the driver is asked to extend a hand in front, palm upwards. The other hand is then placed on top of the first hand, palm downwards. The driver then ‘pats’ the lower hand with the upper hand by rotating it, so that first the lower hand is patted with the palm of the upper hand and then with the back of the upper hand.

In most states if a driver is suspected of DUI driving under the influence of drugs or alcohol, some form of chemical test, such as breath, blood, or urine testing is required. While these tests are technically voluntary, refusal carries a possible penalty such as suspension of driving privileges. A Breathalyzer unit may be used, which is a small hand-held device that measures the driver’s blood-alcohol concentration (BAC). This may be done roadside, at the detainment center, or at a hospital. Blood or urine tests can also be done at a hospital.


You have a right to refuse to perform all field sobriety testing with the exception of the portable PAS breath test. You must perform the PAS breath test when asked and must also submit to a breath or blood test when requested or you will lose your license for one year or longer if you have priors. However, all of the physical tests that a police officer may want you to do are not required. These tests consist of walking a straight line heel to toe, closing your eyes and estimating 30 seconds, the nystagmus test (following a pen or light with your eyes), and any other hop on one foot, jump through a hoop test the officer wants you to do. These tests are only going to be used to try and prove you guilty of a DUI. Performing them will rarely if ever allow you to leave without blowing into a PAS machine and if the PAS reads .08 or higher, you will be arrested and the FST's will be used to prove the blood alcohol machines are accurate by showing impairment.