Field Sobriety Tests 101

If you’ve spent any time watching TV, you’ll have seen someone go through some sort of acrobatics that Hollywood tries to pass off as a test the police use to see if someone is drunk driving. In reality, well-trained police officers use standardized tests to help them determine whether they have probable cause to place a person under arrest for driving under the influence of alcohol, drugs, or both. That’s why the tests are called field sobriety tests—they help law enforcement officers make a decision on the roadside. These tests should be uniform across the country and based on laboratory-verified scientific studies; however, many departments utilize non-standardized tests to help their officers in the field. This creates a confusing maze of all kinds of tests, ranging from the simple to the bizarre. A person facing a DUI charge will need help navigating the legal problems that arise when officers utilize non-standardized tests to try and prove their case. An experienced attorney knows how to spot problems with field sobriety tests and that can provide you or a loved one with a defense to a DUI charge.

Probable Cause

The name of the game is probable cause. Field sobriety tests help give an officer a reason to arrest a driver. Probable cause is the legal standard for whether a police officer can place someone under arrest for DUI/DWI. It’s also a really low legal standard. It has been defined a number of ways, but generally, probable cause is “when there is a reasonable basis for believing that a crime may have been committed.” Before becoming an officer, police go through extensive training, spending months learning the law and investigation tactics. A significant portion of this training is dedicated to DUI investigations and forming probable cause specific to this one type of crime. So, if a police officer is asking you to do field sobriety tests (or FST for short), you are likely dealing with a trained professional who is looking for a “reasonable basis” to arrest you.

Standardized v. Non-standardized

There are two types of FST: standardized and non-standardized. A standardized FST is one that is approved and regulated by the National Highway Traffic Safety Administration (NHTSA). The NHTSA is a government body that addresses all things involving highways—from speed limits to the pavement, the NHTSA knows roads. Included in this broad responsibility is the creation of standardized field sobriety tests. They are called standardized because NHTSA developed a laboratory program to create a science-based approach in giving officers training in how to identify a driver who is under the influence of some intoxicant. The NHTSA is responsible for making sure police departments across the country train their officers in these standardized FST.

There are other tests, however, that are not NHTSA-regulated. These tests vary wildly and can involve reciting the alphabet to counting backward to clapping hands—the list continues to grow. Unfortunately, these tests are not regulated so there is very little data to support them as reliable for helping an officer form probable cause. A defense attorney should be trained to spot the difference between standardized and non-standardized field sobriety tests in order to best defend a client during a DUI trial.

The Standardized Tests

As part of its duties, NHTSA began research on how to determine if a driver is impaired by an intoxicant. This research led to three standardized FST:

  1. Horizontal Gaze Nystagmus (HGN);
  2. Walk and Turn (WAT); and
  3. One-leg Stand (OLS)

These three tests—we’ll call them SFST for “standardized field sobriety tests”—are highly structured. An officer is supposed to give the instructions word for word from NHTSA training and to look for specific indicators, called cues or clues, to see if a person passes or fails the test. Once a certain number of cues/clues are observed, the officer can form probable cause to arrest the driver. The officer is looking at the driver the entire time they are interacting—looking for balance issues, whether the driver is following instructions, checking for soiled clothes, and smelling for alcohol. A driver can give a clue for being intoxicated simply by starting the test before being told to, or for slightly swaying, or even for not exactly touching their heel to their toe. There are more ways to fail these tests than there are to pass them.

Non-standardized Tests

As mentioned above, many police departments utilize non-standardized FST. These are tests that are not regulated by NHTSA and have little to no scientific basis to them. A common set of non-standardized FST are:

  1. Alphabet Test
  2. Counting Test
  3. Fingertip Test

The first two involve having a driver recite the English alphabet or numeric system beginning at a certain letter or number and going to another letter or number—either forward or backward. The Fingertip Test requires a driver to touch their fingertips with their thumb tip in a certain order. These tests vary significantly in how they are instructed and what an officer is looking for in terms of cues or clues. Problems with these “tests” include language issues—English may not be a person’s first language—or learning disabilities—such as dyslexia—that could affect results. Some people are not flexible enough to touch their fingertips or have injuries or they’re cold—the list goes on. These tests are unreliable, have no scientific basis, and police should not utilize them.


In many states, including Virginia, a fourth test is offered: the Preliminary Breath Test, or PBT. This is a handheld device that measures alcohol levels in a person’s breath. It is done on the roadside and quickly produces an estimated blood alcohol level with just a short, strong breath. By Virginia law, the PBT results cannot be used at trial. Police are required to tell a person that the PBT is optional and that it cannot be used at trial. Often, however, police do not follow the PBT law and tell a person that they have to take the test or that the test cannot be used against them in court. This statement is wrong because the PBT can be used in court if the person’s attorney challenges the probable cause for the arrest—the officer would be allowed to testify to the alcohol results from the test only to show that the officer had probable cause for the arrest. A driver, however, is allowed to refuse the PBT and their refusal cannot be used against them at trial.

What is scarier for drivers is that if the PBT shows any amount of alcohol—even if it is under 0.08, the level the law presumes a person to be under the influence—the law allows the officer to arrest that driver for DUI! So, if a driver takes all the FST and pass them but takes the PBT and blows a 0.03, the law says that the driver can be arrested for DUI. Virginia law specifically says that “whenever the breath sample analysis indicates that alcohol is present in the person’s blood, the officer may charge the person with [DUI].” Va. Code Ann. 18.2-267(D). This is the same code section that requires the police to tell a citizen of their right to take or to refuse to take the test. The Virginia appeal courts, however, have basically thrown out this requirement and allow the police to “forget” to tell a person they can refuse the test or that it can, in fact, be used in court (just not trial) to prove probable cause.

Do I Have To Take These Tests?

So hypothetically, let’s assume for a moment that you’ve had a couple glasses of wine with dinner and you’re driving home. You see blue lights—you’re getting pulled over! The officer approaches and says that your car was swerving. She asks if you had anything to drink. What do you do?

Well, in short, you do not have to answer any questions the police ask you except for your name and identifying information. You have a constitutional right to remain silent.

Let’s assume you forget that right for a moment and tell the officer you had a couple of glasses of wine. She asks you to step out of the vehicle to perform some tests.

Does a driver have to take those tests?

No! Field sobriety tests are optional and the courts have routinely held that drivers do not need to take them. The same with the PBT—a driver does not have to take a PBT. Without field sobriety tests or a PBT, an officer will be hard-pressed to have probable cause to arrest someone for DUI.

If you find yourself charged with DUI, you need an experienced attorney to help you fight the case. Our firm has attorneys with years of experience trying DUI cases, including a former prosecutor who has advanced training in all kinds of DUI cases and can spot problems with field sobriety tests. Call us today for a free consultation.

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