California’s DUI Law – Primer On Field Sobriety Tests In Orange County And Beyond

Standardized Field Sobriety Tests (“SFST”) are a battery of tests administered by law enforcement agents to individuals suspected of driving while intoxicated and are designed to detect specific signs of impairment commonly known as “clues.” SFST’s were developed from research sponsored by the National Highway Traffic Safety Administration and performed in the 1970’s at the Southern California Research Institute. The three most commonly SFST’s used are the Horizontal Gaze Nystagmus Test, the One-Leg Stand Test, and the Walk and Turn Test.

Horizontal Gaze Nystagmus Test
Horizontal Gaze Nystagmus (“HGN”) is the involuntary jerking of an individual’s eye that occurs naturally as it moves to the side. Generally, nystagmus occurs only when the eye rotates at high peripheral angles. Alcohol impairment exaggerates nystagmus, causing it to occur at lesser angles and making it difficult for the eye to smoothly track a moving object.

In the HGN test, the tester observes the eyes of the subject as he or she follows a slowly moving object such as a pen or flashlight horizontally. The examiner is watching for three distinct clues in each eye:
1. Is the eye following the moving object smoothly?
2. Is the eye jerking at the maximum deviation, which is the farthest point it can move to the side?
3. If there is jerking, is the angle at which it begins within 45 degrees of center?

If the tester observes four or more clues, the subject is presumed to have a blood alcohol content of 0.08 or greater. The HGN test is often challenged based upon the fact that it fails to account for certain health conditions, such as hypertension, glaucoma, or inner ear problems that can affect an individual’s performance on the test. In addition, substances such as aspirin, caffeine, and nicotine can cause the eye to exhibit nystagmus.

One Leg Stand Test
The One Leg Stand Test (“OLST”) is often referred to as a “divided attention” test. This means that under normal circumstances, the test should be easily performed by most people, however, an impaired individual will have difficulty with the required tasks because they have problems dividing their attention between both mental and physical exercises. In the OLST, the individual is instructed to stand with one foot approximately six inches off the ground and count aloud by thousands until told to put the foot down. The test is timed for 30 seconds while the tester looks for four clues of impairment:
1. Swaying while balancing.
2. Using arms to balance.
3. Hopping to maintain balance.
4. Putting the foot down.

If the tester observes two or more clues, the individual is presumed to have a blood alcohol content of 0.08 or greater. The OLST is often criticized because it can be negatively affected if administered on uneven surfaces, at night, or on a surface with no actual line to walk. Further, the test is unsuitable for people with back or leg injuries, individuals older than 65, and those with inner-ear disorders.

Walk and Turn Test
The Walk and Turn Test (“WTT”) is also a divided attention test. In the WTT, the individual is instructed to take nine steps, heel-to-toe, along a straight line, turn on one foot and return in the same manner to the beginning point. In the WTT, there are eight clues of impairment:
1. Poor balance while listening to the instructions.
2. Beginning before instructed to do so.
3. Stopping to regain balance.
4. Failing to touch heel-to-toe.
5. Stepping off the line.
6. Using arms to balance.
7. Making an improper turn.
8. Taking an incorrect number of steps.

If the officer observes two or more clues, the individual is presumed likely to have a blood alcohol content of 0.08 or greater. The WTT, like the OLST, can be affected by the surface it is conducted on as well as various health conditions afflicting the subject.

The effectiveness of SFST’s to detect intoxication generally depends on the examiner’s observance of the standardized procedures for test administration and scoring. The National Highway Traffic Safety Administration has published materials describing ideal conditions for the administration of SFST’s. These materials also recognize that ideal testing conditions do not always exist in the field. Less-than-ideal conditions and errors in the administration SFST’s affect the weight such evidence should be given.


The bottom line is that SFSTs are wrong and experienced legal counsel can challenge the admission and validity of SFST’s in DUI cases. If you have been charged with DUI in our area, contact Attorney Lauren K. Johnson today.

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