Field Sobriety Tests in Missouri: Are They Mandatory and Should You Take Them?

It’s 11:00 PM on a Saturday. You’ve been pulled over in St. Louis or Jefferson City, and the officer suspects you’ve been drinking. After handing over your license, the officer asks you to step out of the vehicle to “make sure you’re okay to drive.” They want you to follow a pen with your eyes, walk a straight line, or stand on one leg.

Your stomach drops. You feel like you have to say yes to prove your innocence. But do you?

One of the most common questions our DWI defense attorneys get at Rosenblum Robbins Law Firm is: “Do I have to take the field sobriety tests?”

The answer is no . And in many cases, you shouldn’t.

Field Sobriety Tests vs. Chemical Tests It is critical to understand the difference between Standardized Field Sobriety Tests (SFSTs) and Chemical Tests (breathalyzer, blood, or urine).

• Field Sobriety Tests are voluntary. There is no Missouri law that requires you to perform the Walk-and-Turn, the One-Leg Stand, or the Horizontal Gaze Nystagmus (eye) test. You can politely refuse these without facing an automatic license suspension for the refusal itself.
• Chemical Tests are mandatory (under Implied Consent). Once you are arrested, Missouri’s “Implied Consent” law kicks in. Refusing a breath or blood test after arrest can result in an automatic one-year revocation of your driver’s license, regardless of whether you are convicted of the DWI.

Field Sobriety Tests are voluntary. There is no Missouri law that requires you to perform the Walk-and-Turn, the One-Leg Stand, or the Horizontal Gaze Nystagmus (eye) test. You can politely refuse these without facing an automatic license suspension for the refusal itself.

Chemical Tests are mandatory (under Implied Consent). Once you are arrested, Missouri’s “Implied Consent” law kicks in. Refusing a breath or blood test after arrest can result in an automatic one-year revocation of your driver’s license, regardless of whether you are convicted of the DWI.

Why You Might Want to Refuse the Field Sobriety Test Field sobriety tests are designed to gather evidence against you, not to clear you. They are subjective, difficult to perform even when sober, and highly sensitive to external factors.

Here is why even sober drivers often fail:

• Nerves: Anxiety can cause shaking or trouble balancing, which looks like intoxication to an officer.
• Medical Conditions: Bad knees, back problems, or being overweight can make the “One-Leg Stand” impossible.
• Road Conditions: Gravel on the side of a Jefferson City highway or uneven pavement in downtown St. Louis can cause you to stumble during the “Walk-and-Turn.”
• Poor Instructions: If the officer explains the test too quickly, your confusion can be marked as a “clue” of impairment.

Nerves: Anxiety can cause shaking or trouble balancing, which looks like intoxication to an officer.

Medical Conditions: Bad knees, back problems, or being overweight can make the “One-Leg Stand” impossible.

Road Conditions: Gravel on the side of a Jefferson City highway or uneven pavement in downtown St. Louis can cause you to stumble during the “Walk-and-Turn.”

Poor Instructions: If the officer explains the test too quickly, your confusion can be marked as a “clue” of impairment.

What Happens If I Refuse? If you refuse the field sobriety tests, the officer may still arrest you if they believe they have other probable cause (like the smell of alcohol, slurred speech, or erratic driving). However, by refusing, you limit the evidence the prosecution has against you. Without the video footage of you stumbling or failing to follow complex instructions, the state’s case becomes much harder to prove.

The Bottom Line Politely declining a field sobriety test is your right. You can simply say, “I respectfully decline to participate in any field sobriety tests.”

If you have already taken the tests and were arrested, all is not lost. An experienced DWI lawyer can challenge the validity of the tests, the officer’s instructions, and the grading of your performance.

Need Help with a DWI in Missouri? A DWI arrest doesn’t have to mean a conviction. At Rosenblum Robbins, we scrutinize every detail of the stop, from the flashing lights to the final report. If you’re facing charges in Columbia, Jefferson City, or St. Louis, contact us today for a consultation.