Field Sobriety Tests, or FSTs, are usually administered at the scene of the arrest.

The purpose of these tests is for the police

  1. to determine sobriety
  2. to develop probable cause for an arrest
  3. to show that the driver was under the influence at the time of the stop
  4. to gather evidence for the prosecution to build a case against the accused.

The California Highway Patrol utilizes 10 FSTs for determination of sobriety; however, the following three FSTs, now referred to as the Standardized Field Sobriety Tests (SFST) are considered the most sensitive and efficient as a result of a comprehensive correlation study conducted by the Southern California Research Institute in 1981 for the US, Department of Transportation entitled, Development and Field Test of Physiological Tests for DUI Arrest (D0T-HS-9·01970)


Also known as the “Walk-the-Line” test or the “Walk-and-Turn” test, this test is the most common of all the Field Sobriety Tests

The Heel-to-Toe test combines two tasks:

  • Standing on a line (can be imaginary straight line) heel-to-toe.
  • Maintaining balance while walking a line heel-to-toe.

The Heel-to-Toe test is an excellent test for divided attention impairment testing the subject’s ability to process information. Divided attention impairment involves a person’s ability to perform 2 or more acts — both mental and physical –at one time. It is widely accepted that balance and coordination are affected after the primary mental functions need for driving are affects. Consequently, when balance and coordination (physical acts) have been impaired by alcohol, a person’s ability to process information, divide attention, and assess performance (mental acts) has already been impaired also.

This test requires a division of attention between five tasks:

  1. Maintaining a heel-to-toe position with arms at side while listening to instruction.
  2. Maintaining balance while walking a straight line heel-to-toe
  3. Keeping arms at sides.
  4. Counting steps aloud.
  5. Maintaining balance when turning to change direction.

Test Instructions

  • The suspect should put one foot on the line and the other foot behind it with the heel touching the toe.
  • When the suspect assumes this position, the officer should continue with instructions. The subject should then be told to take a pre-instructed number of heel-to-toe steps down the line, turn around and take a pre-instructed number of heel-to-toe steps back.
  • The suspect should keep his/her hands at their sides, watch their feet at all time, and count each step aloud. The officer should ensure the subject understands the direction prior to continuing. The subject should begin and count the first step form the heel-to-toe position as “one.”
  • The suspect should make the turn by keeping one foot on the line and then use the other foot to step around.

Symptoms of Intoxication

  • Loses balance during instructions by not maintaining heel-to-toe position throughout instructions.
  • Starts before instructions are completely explained.
  • Stops while walking or pauses for several seconds after a stop.
  • Does not touch heel-to-toe or leaves a gap between heel and toe on any step.
  • Subject steps to the side (off the line) in order to maintain balance
  • Raises arms to balance.
  • Loses balance while turning.
  • Takes more or less than the pre-instructed number of steps in each direction,
  • Cannot do the test. Steps off the line several times, is in danger of falling, or otherwise demonstrates inability to complete the test.

Leg Raise

Also known as the “Standing on One Foot” test or tile “One-leg Stand” test.

Test Instructions

  • The suspect should be told to stand with his/her heels and toes together, arms down at their sides, raise one foot approximately six inches off the ground, and hold that position for approximately 30 seconds while counting from 1001 to 1030. A high-tolerance drinker at a BAC below 0.15 percent may be able to maintain his/her balance for 20-25 seconds but will likely falter after that time period; thusly, it is recommended that the suspect count aloud from 1001 to 1030 in order to estimate 30 seconds.
  • The officer should demonstrate the test, ensure that the suspect understands the directions, and should not continue until the subject indicates understanding.

Symptoms of Intoxication

  • Sways side-to-side or back-and-forth while balancing.
  • Raises arms to balance.
  • Able to keep one foot off the ground, but resorts to hopping to maintain balance.
  • Puts foot down one or more times during 30-second count; not able to maintain one leg stand position.

Horizontal Gaze Nystagmus

This is one of the most sensitive FSTs available. By using this test it is possible for a trained officer to estimate a suspect’s BAC within plus or minus 0.02 percent of the chemical test results, but the test does have limitations. These limitations are why it is to be used in conjunction with other accepted FSTs.

Nystagmus is the rapid involuntary oscillation of the eyeballs. This oscillating movement may be horizontal, vertical, rotatory, or mixed. Nystagmus may be due to causes other than alcohol. These other causes include seizure, medications, phencyclidine, inhalants, barbiturates, and other depressants. A large disparity between the performance of the right and left eye may indicate brain damage Nystagmus as it relates to alcohol is Horizontal Gaze Nystagmus. It occurs in approximately 50% of all individuals without alcohol ingestion if they move their eyes to the lateral extremes (45% to 65% from straight ahead); however, after a person consumes alcohol the onset of the Horizontal Gaze Nystagmus occurs at a much smaller angel, depending on the BAC As the BAC increases, the lateral extremes usually become very pronounced and smooth pursuit eye movements are interrupted.

Test Instructions

  • Eyeglasses should he removed since they may block the officer’s view of the suspect’s eyes. In addition, hard contact lenses may restrict the boundaries of movement of the eyes, which may prohibit recognition of borderline cases.
  • A stimulus should be positioned slightly above the eyes and about 12-15 inches away. The stimulus can be as simple as the tip of an index finger, a pen or pencil, or a penlight. A penlight makes an excellent stimulus at night. Placing the stimulus slightly above the eyes will elevate them and reduce squinting.

Symptoms of Intoxication

  • The inability of the eyes to follow smoothly
  • The angle of onset of Horizontal Gaze Nystagmus
  • The extent of nystagmus at the maximum lateral deviation.

The other FSTs include:


Test Instructions

  • Suspect stands erect with feet together, eyes closed and arms outstretched in a downward position in front of them, at approximately 45 degrees from their body, keeping elbows straight. Alternating left hand and right hand, under the direction of the officer, the suspect bends forearm in from the elbow, attempting to touch the tip o fhis/her nose with the tip of his/her extended index finger.

Symptoms of Intoxication

  • Sways.
  • Opens eyes.
  • Steps out of position.
  • Fails to touch finger-to-nose.

Modified Position of Attention

Test Instructions

  • Suspect stands erect with heels and toes together, eyes closed, head tilted back, hands down at sides. The officer should allow 30 seconds or more to elapse before telling the subject to open his/her eyes. If eyes are opened before the 30 second time elapse the suspect should restart the time.

Symptom of Intoxication

  • Sways.
  • Opens eyes.
  • Staggers out of position.
  • Almost falls.

Walking in a Straight Line

Test Instructions

  • Suspect is directed to walk to a specific point, turn and return.

Symptoms of Intoxication

  • Staggers.
  • Sways side-to-side.
  • Walks slowly.
  • Walks with wide gait (feet are spread wide apart to maintain balance). A “normal gait” is a narrow line with ankles approximately two inches apart as they pass.


Test Instructions

  • First Alternative -> Suspect recites the alphabet. The officer should ascertain the suspect’s education level to ensure ability to perform the test.
  • Second Alternative -> Suspect writes the alphabet on a piece of paper. To enhance evidentiary value, the suspect signs his/her name on the paper. The paper is then attached to the arrest report and retained with the original file.

Symptoms of Intoxication

  • Is not able to correctly recite the alphabet.
  • Is not able to correctly write the alphabet
  • Forgets to date or sign the piece of paper.

Finger Count

Test Instructions

  • The officer should have the subject count using his/her fingers and thumb. The subject should touch tip of index finger to the tip of the thumb and count “one,” then middle finger to thumb and count “two,” and ring finger to thumb and count “three,” and the little finger to thumb and count “four.” The order is then reversed, four, three, two, and one.

Symptoms of Intoxication

  • Is not able to coordinate the finger movements with speech
  • Is not able to count correctly.

Hand Pat

Test Instructions

  • The officer should have the suspect pat the back of one hand into the palm of the other hand and then turn top hand over and pat palm of top hand into palm of other hand. This test should be performed several times slowly at first then increasing to a relatively rapid pace.

Symptoms of Intoxication

  • Is not able to coordinate hand movements as pace increases.
  • Fails to increase pace of hand pat.

Preliminary Alcohol Screening (PAS) Devices:

Test Instructions

  • PAS devices are handheld roadside devices about the size of a pocket calculator that require the suspect to blow into a balloon or a plastic tube about the size of a cigarette. PAS devices are calibrated to give either a pass/fail reading (set at either .05% BAC for no presumption but the collection of other corroborative evidence or .08% BAC for a presumption of intoxication) or a digital readout of the estimated BAC.
  • Currently, California uses 2 models of Preliminary Breath Testing Devices that are on the National Highway Traffic Safety Administration (NHTSA) Conforming Products List (CPL) for evidential breath measurement devices.
    • I. The Alco-Sensor III
    • II. The Ako-Sensor IV

Symptoms of Intoxication

  • PAS device gives a fail reading
  • PAS device gives a digital readout of an estimated .08% or greater BAC

Related Links

Standardized Field Sobriety Testing
Part Five of this report developed by the National Highway Traffic Safety Administration of the U.S. Department of Transportation outlines the Federal standards for the administration of FSTs.

Quality Three Wholesale, LLC..
Quality Three Wholesale, LLC.sells the handheld AlcoHawk breath alcohol tester, which is the first breathalyzer approved by the Department of Transportation (DOT) and National Highway Traffic Safety Administration (NHTSA) designed and reasonably priced for personal use.

KeRo Corporation
KeRo sells the Alcohol Alert vending machine, which is coin/token-operated breath alcohol tester, to bars, restaurants, ect.

Intoximeters, Inc.
Intoximeters, Inc is the manufacturer of the Alco-Sensor line of breath alcohol testers.

Draeger Safety, Inc.
Draegar Safety, Inc. is the manufacturer of the Alcotest line of breath alcohol testers as well as the Draegar Interlock system for in-vehicle use or wherever it is deemed necessary to prevent an alcohol impaired person from operating a motor vehicle. These devices are commonly referred to as breath alcohol ignition interlock devices (BAIIDs).

CST, Inc.
CST, Inc. is the manufacturer of the line of LifeSafter Interlock systems for in-vehicle use or wherever it is deemed necessary to prevent an alcohol impaired person from operating a motor vehicle. These devices are commonly referred to as a breath alcohol ignition interlock devices (BAIIDs).