How accurate are field sobriety tests (FSTs)?
However, not all FST’s have been scientifically determined to be accurate reflectors of alcohol intoxication. NHTSA has determined that three FST’s are accurate indicators of alcohol intoxication, when administered in a standardized manner. These tests are called Standardized Field Sobriety Tests (SFST’s):
Does the SFST make any mistakes?
The SFST is a test. No test is perfect. All tests make mistakes. Some tests make a lot of mistakes, some make hardly any. But they all make some. Any time any test gives a result, the truth is that result could be correct or it could be exactly and completely the opposite of correct. The SFST makes mistakes.
How accurate is the SFST Test at identifying drunkenness?
Mathematically the accuracy of the SFST test at identifying drunkenness is the same as (actually less than ) the accuracy of an airport security detector test at identifying guns. It makes as much sense to arrest people for being uncoordinated as it does to arrest people for making a metal detector beep.
Why isn't the accuracy of the SFST 91 to 95%?
Over and over scientific research discovered the accuracy of the SFST is 91 to 95%, so why isn't the accuracy of the SFST administered to our defendant 91 to 95%? The quick answer is "accuracy" is more complicated than you think. NHTSA'S "accuracy" statistic is internally valid to the studies, but not externally valid to our case.
When people were guilty, how accurate was this FST?
What journal publishes scientific papers about diagnostic tests?
Does the 76% accuracy statistic work?
Is the 76% accuracy of the NHTSA test accurate?
How accurate is the walk and turn test?
According to the NHTSA, the walk-and-turn test has only a 66% accuracy rate—and that's when it's administered according to their guidelines. If you were charged with DUI after taking the field sobriety tests, it may be possible to call their accuracy into question in an effort to challenge your results.
What is the most accurate field sobriety test?
Tests sponsored by the National Highway Traffic Safety Administration revealed that the HGN test is most reliable (77 percent), followed by the walk-and-turn test (68 percent) and the one-leg-stand test (65 percent).
Is the nystagmus test accurate?
The horizontal gaze nystagmus test is only accurate in about 77% of cases. Reasons for a failed test could include: You suffer from a natural nystagmus in your eyes. You have the flu or an inner ear infection.
Are field sobriety tests scientifically proven?
Of the six or seven roadside tests used in California, National Highway Traffic Safety Administration (NHTSA) has scientifically validated only three for use by officers: the Horizontal Gaze Nystagmus test (HGN), the Walk and Turn test (WAT), and the One Leg Stand test (OLS).
What are the clues for one-leg stand?
While performing this test, the officer will look for six possible clues: swaying, using arms for balance, hopping or putting your foot down. If the officer observes two or more clues, you will fail the test and can be arrested for drunk driving.
What do cops look for in your eyes?
The police officer is looking for specific responses from the eyes that show the driver is under the influence. Nystagmus is the involuntary rapid movement of an eye either horizontally or vertically.
What drugs cause resting nystagmus?
Vertical gaze nystagmus (VGN) Resting Nystagmus is referred to as jerking as the eyes look straight ahead. This condition is not frequently seen. Its presence usually indicates a pathological disorder or high doses of a Dissociative Anesthetic drug such as PCP.
Can you tell if you have nystagmus?
Oscillopsia, or the illusory sensation that the stationary visual world is moving, is the major symptom experienced by patients with nystagmus. When nystagmus is related to a problem involving the vestibular system in the inner ear or the brain, vertigo, dizziness or loss of balance are almost always present.
Is nystagmus a serious condition?
Is nystagmus a serious condition? Nystagmus itself isn't considered dangerous. But it may be associated with serious health conditions, especially those affecting the brain, such as stroke, brain tumor, toxicity, head trauma and inflammatory diseases.
Why do cops have you follow their finger?
The HGN test measures the steadiness of your eyes while you follow an object with your eyes. Officers often use their finger or perhaps a pen for this test because they can easily see your eyes while providing an object for you to follow.
How accurate are Fsts?
Field Sobriety Test Accuracy 10% or higher. After assessing the data, the institute recommended that the horizontal gaze nystagmus, walk and turn and one-leg stand tests be used to test for impairment.
How can you tell if someone is sober?
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....One-Leg Stand TestHopping to maintain balance.Putting the foot down.Swaying while balancing.Using arms to balance.
How accurate are Fsts?
Field Sobriety Test Accuracy 10% or higher. After assessing the data, the institute recommended that the horizontal gaze nystagmus, walk and turn and one-leg stand tests be used to test for impairment.
What are the 3 field sobriety tests?
Field Sobriety Tests refer to standardized tests to initially assess and determine intoxication, namely: the eye test (horizontal gaze nystagmus), the walk-and-turn and the one-leg stand.
How do you tell if you're sober enough to drive?
Here are seven signs that you or a friend could use to help you know if you've had too much to drink to drive:Slurred Speech. Slurred speech is one of the classic signs that you're drunk. ... Trouble with Balance. ... Slowed Reaction Time. ... Unusual Speech. ... Trouble with Recall. ... Failed Field Sobriety Test. ... Try Phone Apps.
How can you tell how drunk you are?
Perform the "walk and turn" test. Stand up straight, then take 9 heel-to-toe steps in a straight line. Turn on 1 foot, then take another 9 heel-to-toe steps back to your starting point. You might be drunk if you had trouble lining up your steps, needed your arms to balance, felt wobbly, or fell over.
How accurate is the SFST?
Most folks find this surprising. It is counterintuitive. Over and over scientific research discovered the accuracy of the SFST is 91 to 95%, so why isn't the accuracy of the SFST administered to our defendant 91 to 95% ? The quick answer is "accuracy" is more complicated than you think. NHTSA'S "accuracy" statistic is internally valid to the studies, but not externally valid to our case. The longer answer is what this web site is about.
What is the mistake the SFST can make?
The SFST makes mistakes. One mistake the SFST can make is to say "guilty" The SFST gave the wrong answer, doesn't mean the scientific test was tricked by driverly imperfection. The lady's HGN wasn't cause by Ménière's disease. Her WAT score wasn't caused by a gimp leg. She is a normal healthy innocent woman, and the SFST mistakenly said she was guilty. The test failed. The SFST was wrong. when the person is innocent. The driver failed the SFST. What does that tell us about her? It tells us she is either guilty or innocent. She's guilty if the imperfect SFST gave the right answer. She's innocent if the imperfect SFST gave the wrong answer. Was our lady's SFST right or wrong? We're back to our theme question: Given that our driver failed the scientific SFST, what is the probability she was impaired by alcohol?
What percentage of DRE officers testify?
DRE officers are trained to testify "93%." Or 91%, or 95%. Those are the SFST accuracies reported in NHTSA's scientific SFST validation studies. They all sound pretty good, which is why defense attorneys don't ask officers the accuracy question.
Is 95% accuracy of SFST valid?
But if that 95% research statistic was calculated using the wrong formula, then in our case it is not valid. The accuracy of our lady's SFST is not 95%. Wow. So what is it? What is the accuracy of the SFST for our lady? The prosecution has no answer. There is no answer. For forty years every time NHTSA has studied the SFST it has used the wrong test accuracy formula. After forty years of un-peer-reviewed, in-house "scientific" projects done by hand-picked contractors with a financial interest in pleasing the agency, NHTSA has provided no scientific basis for stating any percentage as the accuracy of SFSTs done in the field.
Is a test perfect?
No test is perfect. All tests make mistakes. Some tests make a lot of mistakes, some make hardly any. But they all make some. Any time any test gives a result, the truth is that result could be correct or it could be exactly and completely the opposite of correct. The SFST makes mistakes.
Is the Lady's SFST accurate?
As far as the science goes, accuracy of our lady's SFST could by anything. Or nothing. The SFSTs used by US law enforcement are accurate in the same way that astrology, phrenology and palm reading are accurate. They vaguely make sense, and everyone who relies on them seems to think they work.
What Are Field Sobriety Tests?
Field sobriety tests are preliminary roadside evaluations that a police officer may ask you to perform during a DUI stop. If you fail, you may be placed under arrest. Further testing, such as with a breathalyzer, can confirm impairment. Failing one of these evaluations can have a negative impact on your case.
Standardized Field Sobriety Tests (SFSTs)
Although officers may use a combination of different tests, the National Highway Traffic Safety Administration (NHTSA) recognizes three standardized field sobriety tests (SFSTs). These are:
Are These Tests Accurate?
The NHTSA has scientifically evaluated the three standardized tests listed above and have deemed them the most accurate. Under ideal circumstances, officers correctly identified impaired individuals 88% of the time with HGN, 79% of the time with WAT, and 83% of the time with OLS.
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”.
2. Walk and Turn (WAT) Test
The Walk and Turn is a test of divided attention. There are 2 stages of this test:
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.
Call Clyde W. Burleson, P.C., Expert in Field Sobriety Testing
Above all, the science used for Standardized Field Sobriety Tests is flawed. In other words, 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!
What does SFST stand for in DUI?
The information contained in the article is pertinent to DUI offenses across the nation as SFST stands for Standard Field Sobriety Tests which means they are supposed to be standard across the United States. The article was written by a DUI Lawyer.
What is FST in driving?
The National Highway Traffic and Safety Administration (NHTSA) has done extensive studies of field sobriety testing (FST’s) in order to determine the probability of intoxication. Law enforcement agencies have utilized FST’s for many years to develop probable cause for arrest and as evidence to be used in the prosecution for drunk driving. However, not all FST’s have been scientifically determined to be accurate reflectors of alcohol intoxication. NHTSA has determined that three FST’s are accurate indicators of alcohol intoxication, when administered in a standardized manner. These tests are called Standardized Field Sobriety Tests (SFST’s):
What is the accuracy of the HGN and WAT?
The HGN in combination with the WAT reflects an 80% accuracy rate in determining a BAC above .10%.
Why do law enforcement agencies use field sobriety tests?
Because law enforcement agencies use field sobriety testing to establish probable cause in drunk-driving arrests, many people assume that the tests are accurate; however, a number of researchers would argue that these are an unreliable method of determining impairment.
What is the BAC of a SCRI test?
The SCRI brought in 10 officers who watched subjects perform various tests, and asked them to determine whether the test participants had a blood alcohol content (BAC) of .10% or higher.
What was the purpose of the Southern California Research Institute?
During the late 1970s, the National Highway Traffic Safety Administration (NHTSA) tasked the Southern California Research Institute (SCRI) with evaluating the dozens of field sobriety tests that were in use to determine which were the most accurate. The SCRI brought in 10 officers who watched subjects perform various tests, ...
Can you be arrested for drunk driving on the basis of a field sobriety test?
There are expert witnesses who study the field sobriety tests, and understand their weaknesses. Any person arrested for drunk driving on the basis of a field sobriety test score is encouraged to challenge these tests in an effort to fight their criminal charge.
Is field sobriety test reliable?
Scientists will ar gue that these accuracy rates do not support the reliability of the standardized field sobriety tests. In fact, when these tests are correct, they are only indicative of BAC level, and not ability to drive a car. Overall, the field sobriety tests are not a scientifically proven method upon which to base a DUI charge.
What are the three standardized field sobriety tests?
According to NHTSA, there are only three standardized field sobriety tests (SFST’s): 1.) The horizontal gaze nystagmus; 2.) The walk and turn; and 3.) The one leg stand. These are the only tests that have been validated by NHTSA and should be used by law enforcement in evaluating each potential DUI. It should be noted that these tests were only validated to correlate to a specific blood alcohol content (BAC) and they are not be used to show impairment.
How accurate is the HGN test?
According to the most recent studies, HGN is the most reliable of the tests to determine if a person’s BAC is at or above a .08%. This test was found to be 88% accurate, which means it is inaccurate 12% of the time.
When people were guilty, how accurate was this FST?
See the red circle around 84? In this study when people had a high alcohol level, the FST gave the correct answer 84% of the time. When people were guilty, the accuracy of this FST was 84%.
What journal publishes scientific papers about diagnostic tests?
When the Journal of the American Medical Association (impact factor wise, one of the top three medical journals in the world) publishes scientific papers about diagnostic tests, it requires authors to describe diagnostic test accuracy by reporting the statistics sensitivity and specificity.
Does the 76% accuracy statistic work?
NHTSA's 76% accuracy statistic does not allow us to do this FST, get a result, and know the probability that result was correct. NHTSA's statistic "ac curacy" doesn't work.
Is the 76% accuracy of the NHTSA test accurate?
When we don't arrest people, 93% (green circle) of the non-arrests will be correct, not 76%. And if we go to the airport and use this same FST to screen pilots before they fly, NHTSA's "76% accurate" test will correctly identify 84% (red circle) of the drunk pilots.
Horizontal Gaze Nystagmus (HGN) Test
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. After that, the officer will loo…
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. For instance, a 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” test…
Call Clyde W. Burleson, P.C., Expert in Field Sobriety Testing
- Above all, the science used for Standardized Field Sobriety Tests is flawed. In other words, 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!