How Accurate Are Field Sobriety Tests Results?

 Posted on May 21, 2025 in DUI

Field sobriety tests often play a significant role in DUI cases. Reasonable suspicion must be present for a law enforcement officer to pull you over. Even if the officer observes you leaving a bar at 2:00 a.m. in the morning, he or she may not pull you over unless you commit a traffic infraction.

You must be violating traffic laws in some way– weaving back and forth across the center line, driving extremely slowly or at an excessive speed, running a stop sign, etc. – for the officer to legally pull you over. So, assuming you were driving erratically and were pulled over, the officer now needs probable cause to charge you with DUI.

That probable cause is usually obtained through a field sobriety test unless you are obviously slurring your words or passing out while being questioned. Field sobriety tests are not required, but few people know this, and the officer is unlikely to share that information. If you were arrested and charged with DUI after taking a field sobriety test, it is important that you speak to an experienced Rolling Meadows, IL DUI lawyer.

What Are Field Sobriety Tests?

Law enforcement officers often use physical and cognitive evaluations to determine whether a driver is impaired. Field sobriety tests assess a driver’s ability to follow instructions, coordination, and balance. The problem is that while the tests are standardized, the officer is left to interpret them, making that interpretation extremely subjective.

Officers usually administer the horizontal gaze nystagmus test first, asking the individual to follow a moving object with his or her eyes. An impaired person will have exaggerated jerking eyeball movements and difficulty tracking a moving object. The accuracy of this test depends on the officer’s ability to administer it correctly and interpret the results.

The one-leg stand asks the driver to stand with one foot six inches off the ground, counting aloud until the officer has timed the subject for 30 seconds. If the driver sways while balancing, hops to maintain balance, uses his or her arms to balance, or puts a foot down, the officer may use that as proof of impairment.

The walk-and-turn test consists of nine steps, heel-to-toe, along a straight line, with a turn on one foot and walking back in the same manner. If a driver is unable to maintain balance, uses his or her arms to balance, loses balance while turning, fails to touch heel-to-toe, takes an incorrect number of steps, or begins before the officer's instructions are completed, he or she could be judged impaired, even though the accuracy of this test has been questioned.

Why Could Field Sobriety Tests Be Inaccurate?

Further complicating the issue is that every person brings their own set of issues to the table when engaging in field sobriety tests. An individual’s age, physical condition, weight, and gender all contribute to how well he or she might perform the tests. Prescription medications, physical illnesses, stress illnesses, and even the clothing or shoes worn can determine a person’s performance. External factors like the weather, the surface where the field sobriety tests are administered, and how well the officer is trained in administering them can make a difference in the outcome.  

How Can Medical Conditions or Physical Disabilities Affect the Outcome of Field Sobriety Tests?

Many people have balance issues, as well as physical disabilities or medical conditions that prevent them from performing well on field sobriety tests. Officers are unlikely to take these issues into account, resulting in a flawed interpretation. Stress can also significantly affect field sobriety tests, as most people pulled over for DUI understand the enormity of the situation and are, rightfully, nervous.

Contact an Arlington Heights, IL DUI Lawyer

If you are facing DUI charges, you need an experienced Rolling Meadows, IL DUI attorney from Scott F. Anderson, Attorney at Law who can challenge the results of field sobriety tests. If the field sobriety test is proven to be flawed, then the officer may not have had probable cause to administer a breathalyzer test. Attorney Anderson has more than 25 years of experience practicing criminal law as a prosecutor and now as a defense attorney. Call 847-253-3400 to schedule your free consultation.