young man taking field sobriety test with officer and female watching

A Guide To Field Sobriety Tests

There are two main ways that police officers evaluate a driver’s sobriety:

  • Through the use of a breath test to get a blood alcohol concentration reading
  • Observing a driver’s behavior during field sobriety tests

What is a Sobriety Test?

During a traffic stop, a Wisconsin driver may be subjected to field sobriety tests. Field sobriety tests are administered when law enforcement officials suspect that drivers are operating their vehicles while under the influence of intoxicants like alcohol. If a driver fails a field sobriety test that information may be used against the person in a drunk driving trial.

Law enforcement officials can administer a number of tests to investigate for evidence of intoxication in a driver. Each test serves as a way for law enforcement officials to seek out evidence of intoxication from suspected drunk drivers. However, no field sobriety test is perfect and in some cases, sober drivers are charged with drunk driving when these tests provide inaccurate evidence against them.

The accuracy of field sobriety tests is a highly debated topic. Let’s go over everything you should know about these tests so that if you are asked to take one, you are informed.

Types of Field Sobriety Tests

Walk and Turn Test

This test involves physical movement. During the walk and turn test, the driver must walk in a straight line.
The officer will instruct the driver to:

  • Take nine steps forward
  • Walk heel-to-toe
  • Pivot after taking the nine steps in order to turn around
  • Do the same heel-to-toe walk back toward the officer

During this test, the officer will be focusing on the driver’s ability to balance. They may also pay attention to whether or not you stop walking midway through the line, if you need to use your arms for balance, or if you take the wrong number of steps. This test demonstrates problems with balance and with a suspect's ability to follow an officer's directions.

One-Leg Stand Test

This test also tests the driver’s balance. During the one-leg stand test, the driver must:

  • Stand straight
  • Lift one foot off the ground and hold it
  • Keep their hands at their side
  • Keep their foot off the ground and count until the officer says they can stop

This test has similar indicators of intoxication as the walk and turn test above. The officer may also look to see if the driver is swaying while balancing on their one foot, or if they hop. The one-leg stand tests a suspect's ability to balance and use physical coordination.

Studies have shown that the one-leg stand test is only about 65 percent accurate. Therefore, those who have been charged with drunk driving and facing the potential for serious penalties should consider the best way to put on a convincing criminal defense.

Horizontal Gaze Nystagmus Test

While the two other tests involve the full-body, this test focuses on the driver’s eyes.
During a horizontal gaze nystagmus test (HGN):

  • The officer will hold an object in front of the driver’s face (i.e., a pen).
  • The officer will instruct the driver to follow the object with just their eyes as they move it side to side in front of them.

During this test, the officer will be examining the driver’s eyes and any additional movement. Alcohol makes this type of movement more pronounced. If it is exhibited in a drunk driving suspect it can provide an officer with evidence of impairment. Indicators of intoxication for this test include:

  • Jerky eye movement
  • If the subject moves their head in addition to their eyes
  • The driver’s pupil size (indicating drug use)
  • Any difficulty the driver has following the object

As you can see from these three tests, there is nothing clearly measurable like there is with a breath test and BAC reading. It is purely up to the officer’s discretion to determine whether or not the driver is under the influence.

Factors That Influence Test Performance

The National Highway Traffic and Safety Administration has endorsed three tests for law enforcement officers to use in the event that they suspect individuals of drunk driving. Police officers in Wisconsin use these tests as well as others to judge whether drivers are intoxicated; though NHTSA research suggests that failure to perform on the three mentioned tests does generally indicate intoxication on the part of a driver, no test is infallible and each may subjectively affect or challenge some individuals more than others.

There is a record of sober people failing field sobriety tests. In fact, some research estimates that as many as ⅓ of sober drivers can’t pass field sobriety tests. Multiple circumstances at the time of testing can impact overall results.

Subjectivity in terms of a suspect's physical and mental conditions may greatly influence how a person performs on a field sobriety test. An arrest for drunk driving may result even if a person is fully sober at the time of the field sobriety testing; to overcome the apparent evidence of intoxication that field sobriety tests indicate, people may choose to defend themselves in court to overcome the inaccuracies regarding their conditions noted during their arrests.

Medical Conditions

There are numerous medical conditions that can make it nearly impossible for drivers to pass a field sobriety test.
Some of these conditions include:

  • Arthritis
  • Vertigo
  • Prior head trauma
  • Muscle tremors
  • Anxiety
  • Multiple sclerosis
  • Bad back

When you see those red and blue lights flashing behind you, it’s an incredibly stressful experience - even if you’re sober and following all laws. Many people feel intense anxiety when interacting with the police. This anxiety can end up influencing your performance on field sobriety tests. You may be shaking and unable to focus due to nerves - not alcohol.


While reading the above instructions doesn’t make these tests seem hard to understand, there are many reasons why, in the moment, you may not be clear on what you need to do.
This could be because:

  • The road is loud from all of the other cars and you didn’t hear every instruction
  • The officer did not communicate clearly what you needed to do
  • Any language barrier

Because the officer evaluates how well you follow instructions during the test, a simple misunderstanding may lead the officer to think you’re impaired when really, you just didn’t understand the task.

Your Right To Refuse

At the rate that sober drivers fail field sobriety tests, you may be wondering if you can refuse to participate if asked. The good news is that you can.

Breath tests are covered under implied consent laws, meaning that if you refuse to take a breathalyzer test when asked, you face additional penalties like license suspension.

However, field sobriety tests are not covered by this law. You can refuse to take a field sobriety test for any reason.

Challenging Field Sobriety Tests in WI

You might find yourself wondering how you can push back against police officer testimony and what appears to be scientific evidence. There are defense strategies to attack these aspects of a prosecution's case, but you must know how to do it properly and convincingly.

Field sobriety tests like these are often relied upon by prosecutors to secure a conviction. But the mere fact that a field sobriety test was conducted and an individual "failed" that test does not mean that it is a legitimate indication of a driver's intoxication. After all, the test itself is not 100 percent accurate, and a police officer conducting the test may administer it inappropriately. He or she may even falsely state that he or she saw indications of intoxications during a field sobriety test.

Many people experience medical conditions, such as multiple sclerosis, that could impact their balance. Other health issues, such as a bad back, could also affect a person's performance on such a test.

Other issues related to the environment could also impact a person's performance. If the ground is uneven or the person is wearing shoes to which he or she is unaccustomed, he or she could appear off balance. In some cases, in which allegations are made that a suspect failed a field sobriety test, the issue actually lies with a police officer who did not follow procedure or was not properly trained.

When negotiating or litigating your drunk driving case, you can make arguments that attack the reasons for an initial stop, the way a field sobriety test was conducted, as well as the accuracy of any breath tests. This may mean that you need witnesses of your own, perhaps even expert witnesses, and physical evidence that contradicts that presented by the prosecution.

Sheboygan DUI Defense

Melowski & Singh, LLC is Wisconsin’s most successful DUI defense firm. If you are facing DUI charges after taking a field sobriety test, we can help defend your rights. Give us a call today at (920) 294-1414 so we can set up an appointment to discuss the specifics of your arrest.