Field Sobriety Tests

Field Sobriety Testing

Yuba City, CA DUI Attorney

Standardized Field Sobriety Testing is something that has been developed and approved by the National Highway Traffic Safety Administration. These are standardized test that they authorize for use in the event that an officer pulls a suspect over for drinking and driving. Chemical tests are a tool that can provide greater accuracy to determine if a suspect was drinking or not, but certain forms can be time consuming and officers are not always able to test every person. A SFST is a means for an officer to examine the outward effects of a person and if it appears that they have been altered by a high level of alcohol in their system. SFST include three different tests. These are the Walk-and-Turn, the One-Leg-Stand and the Horizontal Gaze Nystagmus test. They are not fully accurate and can only add to an officer formulating their opinion. Talk to a Yuba City lawyer if you have been arrested.


The Walk-and-Turn test requires that a person walk a certain distance and turn back. They will go a long a straight line, placing one foot in front of the other for nine steps. After they have taken these steps, they will then need to turn around and come back while following the same rules. This test may seem simple but for those that have alcohol in their system it can be challenging to balance or even remember the details of what they are supposed to do. An officer will be assessing if the suspect needs to use their arms to balance, steps off the line, does not walk heel to toe, miscounts their steps, makes a wrong turn or does not wait until instructed to start the test. It is believed that this test has an accuracy rate of 79 percent at pinpointing suspects that demonstrate two or more of these signs as having a blood alcohol content level at .08 or more.


The One-Leg-Stand test will require the person in question to balance on one of their legs. This will be for a period of time specified by the officer (30 seconds) and the suspect will need to count by thousands. Their foot should be raised off of the ground by six inches and will remain there until told otherwise. An officer will review if they need to put their foot down, use their arms, hop back and sway back and forth. Those that show two or more of the signs are found to have a BAC level of .08 or above 83 percent of the time.

Horizontal Gaze Nystagmus (HGN)

HGN testing assesses for Horizontal Gaze Nystagmus. The eye has a natural tendency to involuntarily jerk in certain situations. When alcohol is in the system of a person this can be altered and may become more exaggerated. Horizontal Gaze Nystagmus causes the jerking of the eye to happen at earlier angles when the eye it rotated around. An officer can inspect a suspects eyes and will perform three tests on each eye. They can use an object such as a flashlight or pen to carry out this test. The three things they will look for include how smooth the eye transitions, if jerking occurs when the eye is deviated to the side and what the angle is at which the jerking occurs. This test has been determined by the NHTSA to have an accuracy rate of 88 percent.

Officers are not only assessing the outward physical signs of alcohol impairment through SFSTs. They are also observing the comprehension of a person. If they are able to hear the instructions given, process them and carry them out. Balance, coordination and control are also very important since these are areas of a person that higher amounts of alcohol will affect. While these tests are given an accuracy rate alone, they are expected to increase in their effectiveness when an officer administers more than one of them when assessing if an individual is driving while intoxicated.

Unfortunately the findings of this test can be altered for various reasons and an innocent person can be perceived as guilty. This may be an officer that is not properly trained on how to administer the test, a medical condition or even the bright lights of the cars on the street influencing a person that is being tested for HGN. The courts understand the field sobriety tests can have errors so they will generally not take the findings of them as purely fact. It is important to be able to demonstrate why the findings of these are false since they will often still be highly considered in a DUI charge.

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