Table of ContentsView AllTable of ContentsField Sobriety Test TypesSigns of IntoxicationCan You Fail if You’re Sober?Marijuana and Other SubstancesTest Refusal
Table of ContentsView All
View All
Table of Contents
Field Sobriety Test Types
Signs of Intoxication
Can You Fail if You’re Sober?
Marijuana and Other Substances
Test Refusal
This article discusses the three types of field sobriety tests that may be administered and the essential information you should know about these DUI tests.
The Three Field Sobriety Tests
National Highway Traffic Safety Administration defines and describes the three parts of the field sobriety test in detail. If the driver fails any of the field sobriety tests, the officer will then ask the suspect totake a breath testor a chemical test to confirm their blood-alcohol content.
The Standard Field Sobriety Test (SFST) is a battery of three tests that include the horizontal gaze nystagmus (HGN), the walk-and-turn, and the one-leg stand tests.
Horizontal Gaze Nystagmus
Horizontal gaze nystagmus is an involuntary “jerking” of the eyeball which happens to everyone when the eyes are rotated at high peripheral angles. When a person is intoxicated, however, the jerking of the eyes becomes more exaggerated and occurs at lesser angles.
Turning the HGN test, the officer will ask the driver to follow a moving object, such as a pen or flashlight, slowly from side to side. The officer looks to determine:
If four or more clues appear between the two eyes, the driver is likely to have ablood-alcohol content(BAC) 0.10 or greater. Research from the NHTSA shows this test to be accurate in 77% of test subjects.
Walk-and-Turn Test
For the walk-and-turn test, the officer asks the driver to take nine steps, heel-to-toe, along a straight line, turn on one foot and return nine steps in the opposite direction. During the test, the officer looks for seven indicators of impairment. A subject may be impaired if they:
According to the NHTSA, if the driver exhibits two or more of these indicators during the test, there is a 68% likelihood of a BAC level of 0.10 or higher.
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One-Leg Stand Test
For the one-leg stand test, the officer asks the driver to stand with one foot about six inches off the ground and count from 1,001 (one-thousand-one, one thousand two, etc.) until the officer says to put the foot down. During the next 30 seconds, the officer looks for these four indicators:
If the driver exhibits two or more of the above indicators, there is a 65% chance they have a BAC of 0.10 or greater, according to the NHSTA.
If you suspect that you or someone else might be intoxicated, there are some signs to watch for. Indicators that someone is drunk and may fail a field sobriety test include:
Alcohol affects people differently. Even if you don’t feel drunk, do not operate a motor vehicle if you have been consuming alcohol.
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Can You Fail a Field Sobriety Test While Sober?
There are many reasons that people who are not intoxicated might not be able to perform the above tests successfully. These include certain medical conditions, disabilities, age, injury, and taking a certain medication.
The officer usually will ask the driver if there is a reason that they may not be able to pass the test and makes a note of their answer in the arrest report.
If there is a legitimate reason, medical or otherwise, why you might fail one or more parts of the field sobriety test, make sure you mention it so that the officer notes it in the official record. It might be helpful to you in court later.
Tests for Marijuana and Other Substances
Field sobriety tests can be used to check for signs of intoxication and impairment. However, they cannot determine specifically what substances a person has been using.
HGN tests are commonly used to look forsigns of marijuana intoxication. However, research indicates it is not a reliable tool for detecting cannabis use.Officers may also look at the individual’s pupils to see if they are unequal, have unusual movements, or are extremely dilated or constricted.
Laws about driving under the influence of cannabis vary. Some states utilize “per se” laws similar to alcohol intoxication, suggesting that a certain level ofTHC(the psychoactive compound delta-9-tetrahydrocannabinol) corresponds to alcohol intoxication.
However, research indicates that specific THC levels do not correlate with specific levels of impairment. Even low levels of THC may cause significant cognitive and psychomotor impairments.
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Can You Refuse a Field Sobriety Test?
While you have a right to refuse a field sobriety test orbreathalyzer test, the state also has a right to penalize you for doing so.
A field sobriety test helps provide evidence that an individual is intoxicated. If someone refuses the tests, however, police can still arrest a person that they believe is intoxicated and then conduct further testing. They can also still arrest someone who passes field sobriety tests if they suspect the individual is under the influence.
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5 SourcesVerywell Mind uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Stuster J.Validation of the standardized field sobriety test battery at 0.08% blood alcohol concentration.Hum Factors.2006;48(3):608-14. doi:10.1518/001872006778606895National Highway Traffic Safety Administration.Instructor Guide DWI Detection and Standardized Field Sobriety Testing Refresher.Bond J, Witbrodt J, Ye Y, Cherpitel CJ, Room R, Monteiro MG.Exploring structural relationships between blood alcohol concentration and signs and clinical assessment of intoxication in alcohol-involved injury cases.Alcohol Alcohol. 2014;49(4):417–422. doi:10.1093/alcalc/agu014Celeste MA.A judicial perspective on expert testimony in marijuana driving cases.J Med Toxicol. 2017;13(1):117-123. doi:10.1007/s13181-016-0579-zNational Institute of Justice.Field sobriety tests and THC levels unreliable indicators of marijuana intoxication.
5 Sources
Verywell Mind uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Stuster J.Validation of the standardized field sobriety test battery at 0.08% blood alcohol concentration.Hum Factors.2006;48(3):608-14. doi:10.1518/001872006778606895National Highway Traffic Safety Administration.Instructor Guide DWI Detection and Standardized Field Sobriety Testing Refresher.Bond J, Witbrodt J, Ye Y, Cherpitel CJ, Room R, Monteiro MG.Exploring structural relationships between blood alcohol concentration and signs and clinical assessment of intoxication in alcohol-involved injury cases.Alcohol Alcohol. 2014;49(4):417–422. doi:10.1093/alcalc/agu014Celeste MA.A judicial perspective on expert testimony in marijuana driving cases.J Med Toxicol. 2017;13(1):117-123. doi:10.1007/s13181-016-0579-zNational Institute of Justice.Field sobriety tests and THC levels unreliable indicators of marijuana intoxication.
Verywell Mind uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
Stuster J.Validation of the standardized field sobriety test battery at 0.08% blood alcohol concentration.Hum Factors.2006;48(3):608-14. doi:10.1518/001872006778606895National Highway Traffic Safety Administration.Instructor Guide DWI Detection and Standardized Field Sobriety Testing Refresher.Bond J, Witbrodt J, Ye Y, Cherpitel CJ, Room R, Monteiro MG.Exploring structural relationships between blood alcohol concentration and signs and clinical assessment of intoxication in alcohol-involved injury cases.Alcohol Alcohol. 2014;49(4):417–422. doi:10.1093/alcalc/agu014Celeste MA.A judicial perspective on expert testimony in marijuana driving cases.J Med Toxicol. 2017;13(1):117-123. doi:10.1007/s13181-016-0579-zNational Institute of Justice.Field sobriety tests and THC levels unreliable indicators of marijuana intoxication.
Stuster J.Validation of the standardized field sobriety test battery at 0.08% blood alcohol concentration.Hum Factors.2006;48(3):608-14. doi:10.1518/001872006778606895
National Highway Traffic Safety Administration.Instructor Guide DWI Detection and Standardized Field Sobriety Testing Refresher.
Bond J, Witbrodt J, Ye Y, Cherpitel CJ, Room R, Monteiro MG.Exploring structural relationships between blood alcohol concentration and signs and clinical assessment of intoxication in alcohol-involved injury cases.Alcohol Alcohol. 2014;49(4):417–422. doi:10.1093/alcalc/agu014
Celeste MA.A judicial perspective on expert testimony in marijuana driving cases.J Med Toxicol. 2017;13(1):117-123. doi:10.1007/s13181-016-0579-z
National Institute of Justice.Field sobriety tests and THC levels unreliable indicators of marijuana intoxication.
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