Are Field Sobriety Tests Sufficient Probable Cause for Arrest?

 Posted on March 12, 2025 in DUI

A police officer must have reasonable suspicion that a driver is impaired before pulling him or her over by personally witnessing the driver driving erratically in some way. If there is reasonable suspicion to pull over a driver, then there must be probable cause for an arrest. This means that before making a DUI arrest, the police officer must have probable cause to believe the driver is driving under the influence or sufficient evidence that the driver has "probably" committed the crime of DUI.

Officers usually get this probable cause by asking the driver questions to see if his or her words are slurred, eyes red and watery, or if there is a strong smell of alcohol coming from the driver. If questioning the driver leads the officer to believe he or she is intoxicated, the officer may ask the driver to perform field sobriety tests to be sure before an arrest is made.  While field sobriety tests are used in every state – but are not mandatory in any state – they are often less than accurate yet can be used as evidence in court to prove an individual was driving under the influence.

At best, field sobriety tests rely on the officer’s subjective judgment yet are admissible in court. At its worst, there is a litany of problems associated with field sobriety tests, including the fact that a person with balance issues who has not had a drop to drink would likely fail field sobriety tests. If you agreed to a field sobriety test and are now facing DUI charges, it is important to speak to an experienced Oakbrook Terrace, IL DUI attorney.    

What Are Field Sobriety Tests?

Standardized field sobriety tests, such as the horizontal gaze nystagmus, the walk-and-turn exercise, and the one-leg stand, help police officers determine whether a driver is impaired. Unfortunately, the accuracy of these tests depends on the consistent application of the test parameters and measurable results. In the walk-and-turn test, the driver must walk heel-to-toe in a straight line for nine steps, turn around, and complete the same walk for nine steps back to the original location. The one-leg stand test requires the driver to lift one leg six inches off the ground, standing on the other leg for at least 30 seconds. The gaze test requires the driver to follow an object with his or her gaze. Field sobriety tests are generally only considered accurate about two-thirds of the time.

What Environmental Factors Affect Field Sobriety Tests?

An officer conducting an FST is looking for "universal" symptoms that would suggest impairment. Since field sobriety tests are never performed in a controlled environment, it is impossible to achieve consistent responses. The brightness of the sun, how the car lights and flashing lights of the police car illuminate the ground at night, sloped surfaces, and the surface's material can all impact the outcome of the tests. If it is unusually hot or cold outside, raining, windy, or there is snow or ice on the ground, these tests become even more unreliable as a measure of impairment. Since most DUI stops occur at night, a person taking field sobriety tests is immediately at a disadvantage.

Individual Responses to Field Sobriety Tests That Can Affect the Outcome

On the most basic level, any person stopped for DUI is going to be stressed and anxious, especially a woman who is stopped by a male police officer at night on a deserted highway. The officer can misinterpret fear or anxiety as signs of impairment. Women may be wearing heels, which can make performing a field sobriety test on a sloped, rocky road at night even more difficult. Drivers who have medical issues or are taking certain prescription drugs, or those who are elderly, are much more likely to have problems "passing" field sobriety tests.

Contact a Chicago, IL DUI Lawyer

If you are facing DUI charges, the best step you can take is to contact a Rolling Meadows, IL DUI attorney from Hartsfield Law. Attorney Hartsfield’s diverse background, including experience representing defendants for the Will County Public Defender’s Office and teaching courses to pre-trial detainees at the Cook County Dept. of Corrections, benefits each of his clients. Call 312-345-1700 today to schedule your free consultation.