skip to Main Content
How Reliable Are Field Sobriety Tests?

How Reliable are Field Sobriety Tests?


When pulled over by an officer there are 3 Field Sobriety Tests that are most commonly used to determine if a person meets the “probably cause for arrest” requirements necessary to sustain an alcohol-impaired DWI conviction. These tests were created by the National Highway Traffic Safety Administration (NHTSA) in the mid to late 1970s and by 1981 police officers began to administer these SFSTs on individuals who were suspected of DWI shortly thereafter. The problem with these three tests is that they are flawed in several ways and do not provide a scientific or consistent determination of intoxication.

1. Horizontal Gaze Nystagmus (HGN) Test


Nystagmus is a condition of involuntary (or voluntary, in some cases) eye movement, acquired in infancy or later in life, that may result in reduced or limited vision. Due to the involuntary movement of the eye, it has been called “dancing eyes”. When a person is inebriated, the jerking movement is greatly exaggerated. This combined with the fact that a person who is intoxicated will have greater difficulty in tracking a moving object. Officers performing a HGN test are looking for 3 clues per eye (6 total) that they can use to determine that you are over the legal blood alcohol content (BAC).

  • Lack of Smooth Pursuit – The eyes are unable to follow a moving object – such as a pen – smoothly.
  • Distinct and Sustained at Maximum Deviation – The jerking of the eye is more apparent when the eye is looking as far into its periphery as possible.
  • Onset of Nystagmus Prior to 45 Degrees – The jerking of the eye is increased when the eye is within 45° of center.

If a test recipient has four or more indicators, they are determined to be inebriated. While the NHTSA manual is extremely specific about what an officer must do when performing this test, it is ultimately a test that is 100% up to the opinion of the arresting officer.

2. Walk and Turn (WAT) Test


The Walk and Turn is a test of divided attention. There are 2 stages of this test:

  1. Instruction Stage – A recipient must stand in a heel-to-toe position with their arms at their sides and listen to the instructions given by an officer.
  2. Walking Stage – The recipient must take 9 heel-to-toe steps, turn, and take another 9 heel-to-toe steps back to the starting point.

The officer will then look for 8 different clues to determine inebriation:

  • Can’t Keep Balance During Instructions
  • Starts Too Soon
  • Stops Walking
  • Doesn’t Touch Heel to Toe
  • Steps Off Line
  • Uses Arms for Balance
  • Loses Balance on Turn / Turns Incorrectly
  • Takes the Wrong Number of Steps

A WAT test recipient only needs to get 2 of these wrong to be considered drunk. Once again, the scoring is completely subjective and 100% up to the opinion of the arresting officer. Additionally, it does not take into account any past or present injuries unless disclosed to the test taker without being prompted.

3. One-Leg Stand (OLS) Test


The One-Leg Stand is another example of a divided attention test. It has 13 different instructions and is also comprised of two stages:

1. Instruction Stage

  • Stand with your feet together and your arms at your side (demonstrate).
  • Maintain position until told otherwise.
  • When I tell you to, I want you to raise one leg, either one, approximately 6 inches off the ground, foot pointed out, both legs straight and look at the elevated foot. Count out loud in the
  • following manner: 1001, 1002, 1003, 1004 and so on until told to stop.
  • Do you understand the instructions?
  • You may begin the test.

2. Testing Stage

There are four cues or clues that a police officer is looking for on the One-Leg Stand Test. Again, failing only 2 clues will be considered failure and evidence of intoxication and impairment.

  • Sways while balancing
  • Uses arms to balance
  • Hops
  • Puts foot down

Much like the first two test, the majority of this is subjective and doesn’t take into account any past or current injuries or even physical condition of the test recipient.

Limitations & Criticism of Field Sobriety Tests


Critics of these test often question the statistical evidence behind them, and the ability of the officers to administer the tests and judge for impairments. One study by Patrick Barone in “Standardized Field Sobriety Testing” asked 14 police officers to view the videotapes of 21 sober individuals being put through a series of both field sobriety tests and “normal-ability” tests such as walking, knowing their address, and similar. After reviewing the test, the officers believed that 46% of the participants has too much to drink. Fifteen percent of the officers viewing the normal-abilities videos thought the individuals had too much to drink.

In another book “Field Sobriety Tests: Are They Designed for Failure?”, the authors concluded that Standardized Field Sobriety Tests (SFSTs) must be held to the same standards the scientific community would expect of any reliable and valid test of behavior, and that Standardized Field Sobriety Tests  should be examined and judged critically.
In fact, the NHSTA initially started with 6 tests as part of their research. Of the 6, only three were chosen as sufficiently reliable and accurate to conduct further studies:

  1. The Horizontal Gaze Nystagmus (HGN) Test – 77% Accuracy

  2. The Walk-and-Turn (WAT) Test – 68% Accuracy

  3. The One-Legged Stand (OLS) Test – 65% Accuracy

Call Clyde W. Burleson, P.C., Expert in Field Sobriety Testing


In the end, it is clear that the science and implementation used for Standardized Field Sobriety Tests is flawed on many levels.  Don’t leave your future in the hands of opinions and pseudoscience posing as fact. Contact Clyde W. Burleson, P.C. and make sure that your rights are being protected!


Back To Top