The National Highway Traffic Safety Administration (NHTSA) began research in 1975, trying to find a standardized test to detect whether a driver was under the influence of alcohol. NHTSA developed tests that were initially designed to detect a blood alcohol concentration (BAC) of 0.10%.
By 1981, most states lowered the legal BAC level to the current 0.08% in North Dakota and Montana, and NHTSA recommended six sobriety tests at that time. The agency later published its Standardized Field Sobriety Test (SFST) battery of three tests in 1999.
Gaze, walk and stand: The three components of SFSTs
While NHTSA argues the tests are 90% accurate when administered by a trained officer, some studies say they have an accuracy rate of 65% to 77%. The three tests are:
Horizontal gaze nystagmus (HGN): The HGN test is measured to gauge an involuntary jerking of the eyeball where an officer shines a light in the driver’s eyes. The motion in intoxicated individuals’ eyes is usually more exaggerated.
Walk-and-turn: The officer will ask a driver to take nine steps heel-to-toe along a straight line, then turn on one foot and walk nine steps in the other direction. There are several indicators officers look for, including:
- Keeping your balance while listening to instructions
- Starting to walk before instructions are given
- Losing balance while walking
- Failing to walk heel-to-toe
- Using arms to maintain balance
- Taking an incorrect number of steps
One-leg stand: An officer will ask a driver to raise one foot six inches off the ground and begin counting upward from 1,001 until they are instructed to put their foot down. For 30 seconds, officers look for swaying, using arms or hopping to maintain balance or putting the foot down prematurely.
Know your rights if charged with DUI
A DUI conviction can have devastating personal and financial effects. In addition to possible jail time, fines and fees and suspended driving privileges, insurance rates can be doubled or tripled, and in some cases, coverage can be denied. An experienced defense attorney will protect your rights by making sure officers had probable cause to stop you and correctly performed field sobriety and chemical testing. A successful defense can result in lower fines, less jail time, or charges being dropped.