We all know the drill. Whenever someone receives field sobriety test, they stand on one foot, walk heel to toe in a straight line, and follow a light with their eyes. However, what you may no know is that field sobriety tests may not be as accurate as you think. Field sobriety tests are the standard for law enforcement officials, but where did they come from and are they accurate in determining someone’s BAC?

What about if you’re suspected of driving under the influence of drugs? How are police trained to detect if you’ve used marijuana while driving? Should you submit to a field sobriety test? In this article, we discuss: 


  • The history of field sobriety tests
  • Accuracy of field sobriety tests
  • Information on marijuana DUI charges
  • Police training 
  • If you should submit to a field sobriety test
  • What to do if you’ve been charged with a DUI

The History of Field Sobriety Tests

Police agencies across the nation haven’t always had standardized field sobriety tests. Also, there was a time in this country where someone drinking and driving wasn’t considered a big deal. In 1975 the National Highway Traffic Saftey Administration set out to change both of these issues. The NHTSA gave the Southern California Research Institute the task of developing standardized field sobriety testing procedures.

The SCRI tested 16 standard police procedures to determine the most accurate tests. They specifically targeted anyone who had a BAC over .10%, not just any impairment. In the end, the researchers settled on the three criteria that are today’s standard. Those tests are the walk-and-turn, the one leg stand, and the Horizontal Gaze Nystagmus test.

These tests are accurate for some people but not accurate for others. Specifically, anyone who has back, leg, or middle ears problems and anyone that is more than 50 pounds overweight. People with these problems may have issues performing the field sobriety tests.

The first test results were less than perfect. There was a 47% margin of error immediately following the implementation of these tests. That’s no small margin of error. Despite these issues with the inaccuracies of field sobriety tests, they’ve continued to be used by law enforcement over the years. 

The Accuracy of Field Sobriety Tests

There have been many studies on the accuracy of field sobriety tests. As with anything the early days were the worst. The learning curve for police officers was steep. A 1981 study reported only 77% accuracy with a 32% false arrest rate. That means a lot of people spent a night in jail that weren’t breaking the law.

In 1994 Dr. Spurgeon Cole of Clemson University set out to test the accuracy of field sobriety tests. In his study police officers performed six tests on 21 subjects. These officers determined that 46% of the subjects were over the legal BAC limit and therefore unable to drive. The only problem is that none of the subjects had any alcohol in their systems. All of the participants BACs were .oo%. The officers would have almost been better off just guessing at random.

Who is at Fault?

Many people just assume that poor study results can be pinned on untrained officers. While this may be the case in some situations, there is a much larger problem, the tests themselves. There is very little scientific evidence that the standardized NHTSA are accurate at all. How do we know? We are aware because the people that made the tests said so themselves.

The SCRI had two cracks at making accurate tests, and both times they failed. As previously mentioned, these tests have been inaccurate since their inception. The SCRI’s test results show the flaws in the current system. The first attempt produced tests that were only accurate 53% of the time and the second attempt increased their accuracy to 80%. Now you may be thinking that 80% is accurate, but as far as science goes, it isn’t even close.

Studies conducted by the NHSTA themselves show a confidence inspiring 91% accuracy. However, these studies were carried out by partial research agencies. The results of these studies don’t give the whole picture. Many of the participants were so far over the legal BAC limit that the tests were irrelevant. The officers were also allowed the use of portable breathalyzers. When determining if a subject was intoxicated, they were allowed to take the results of the breathalyzer into account. These type of tests don’t seem very impartial.

What About Marijuana? 

Providing evidence that a driver is stoned or high when operating a vehicle has become one of the biggest issues that law enforcement faces. When someone smokes or digests marijuana, the THC will stay in their system for days, weeks, or even up to a month depending on the dosage and size of the person. If a driver is pulled over for reckless driving and they’re given a blood test under suspicion of intoxication, it’s very difficult to approach the situation from an objective perspective. If THC is found in the driver’s system, there’s no way of knowing if the driver was high while driving or if this was due to smoking weed days beforehand.

This dilemma has already led to a series of issues with legal cases all over the country in legalized marijuana states. It’s clear how this inability to properly test drivers can result in false convictions of DUIs in New Jersey. In effect, it could lead to a rise in DUI cases but not necessarily legitimate DUI arrests. 


Example of Marijuana Case in New Jersey


While there are many cases of DUI charges in which the driver was found with THC in their system, here’s one specific yet extreme example. After a fatal accident in South Jersey that killed a jogger and the passenger in the vehicle, the driver was given a blood test. This test showed that he had minimal amounts of THC in his system and he was charged with a DUI and two counts of vehicular homicide. The accident happened in 2015. He was acquitted of the charges last year due to lack of evidence that could prove that he was impaired at the time of the accident. Even the National Highway Traffic Safety Administration urges legal experts and analysts to not use blood tests as evidence of impairment. This case and others like it will make it very difficult for prosecutors to identify drugged drivers and legitimate cases of DUIs in New Jersey. 


A Call For More Advanced Training for Police Officers


New Jersey state Senator Nicholas Scutari, a sponsor of the bill to legalize recreational marijuana, has made his opinion about blood tests in DUI cases clear. He states that, “blood tests are rarely used in DUI cases” and tests like breathalyzers or field sobriety tests are more accurate. He believes that drivers who are operating vehicles under the influence “convict themselves with respect to videotape taken by body cams.” Scutari and other legislators who support the bill are claiming that police observation in these circumstances are a much more accurate tool to determine marijuana impairment than a blood test. This is why the bill contains funding for advanced police training. 


In these training procedures, police officers will learn how to detect stoned or high drivers by implementing a number of sobriety tests. Of course, with the inaccuracies of field sobriety tests for alcohol, fears have already been raised about how accurate marijuana field sobriety tests will be. Moving forward, all medicinal marijuana patients should be cautious while driving. There’s a high probability that sober drivers can easily be unfairly charged with these shaky field procedures. 


Should You Take Field Sobriety Tests?

You may think that you have to perform field sobriety tests. However, this is not the case. Police training teaches an officer to make a question sound like a demand. Their training can blur the lines of what is a requirement and what is voluntary. If a police officer pulls you over and suspects that you are above the BAC limit, you should not submit to field sobriety testing. Obviously, you want to be respectful and courteous, but that is all you should do. No matter what an officer tells you, you do not have to submit to any roadside tests. However, an officer may still arrest you, if they have reasonable cause to do so.

New Jersey is known as an implied consent state. This means that you do have to submit to BAC testing by breath, urine, or blood, but this doesn’t include the portable breathalyzer. If an officer arrests you on suspicion of a DUI, it is best to submit to the breath test at the station. Failure to do so will result in an immediate suspension of your license. Breath tests are challengeable in court; refusal, however, is much more difficult to defend. Your New Jersey DUI lawyer can help you with the best defense strategy.


If You’ve Been Charged with a DUI

It’s become quite clear that field sobriety tests are highly inaccurate and shouldn’t be used by law enforcement. In addition, there isn’t a way to measure marijuana use in blood or urine tests and properly apply it as evidence in a DUI case. If and when weed becomes completely legal in New Jersey, those who use the drug will most likely have some level of THC in their system at all times. With the inaccuracies that swarm around drug and alcohol DUI convictions, it’s always important to have an experienced DUI lawyer on your side. If you feel as though you were wrongly convicted of a DUI due to a poorly conducted field sobriety test or drug test, it’s important to call a DUI attorney as soon as possible.