DUI Investigation and Standard Field Sobriety Tests

The Purpose of DUI Investigation

A DUI investigation in Colorado typically begins when a police officer believes they have reasonable suspicion to stop a vehicle. This could involve weaving within a lane, speeding, or even a minor traffic violation such as a broken taillight. Once stopped, the officer begins looking for signs of impairment such as:

• The smell of alcohol or marijuana

• Slurred speech

• Bloodshot or watery eyes

• Difficulty retrieving license and registration

If the officer believes impairment may be present, they often ask the driver to exit the vehicle and perform Standard Field Sobriety Tests (SFSTs). These roadside exercises are standardized nationwide by the National Highway Traffic Safety Administration (NHTSA), but they are not always reliable indicators of impairment.

To understand defense strategies, visit our DUI lawyer guide.

What Are Standard Field Sobriety Tests?

Standard Field Sobriety Tests (SFSTs) are commonly used during Colorado DUI investigations. They are designed to evaluate a driver’s “divided attention,” meaning the ability to perform physical and mental tasks at the same time.. According to NHTSA guidelines, the three standardized tests include:

1. Horizontal Gaze Nystagmus (HGN) Test
   The officer shines a light or pen in front of the driver’s eyes and asks them to follow it. They look for involuntary jerking of the eyes, which is believed to be more pronounced under alcohol influence.

2. Walk-and-Turn Test
   The driver must take nine heel-to-toe steps along a straight line, turn on one foot, and return the same way. Officers look for balance issues, starting too soon, or incorrect steps.

3. One-Leg Stand Test
   The driver raises one foot about six inches off the ground and holds it while counting aloud. If the driver sways, hops, or puts their foot down, it may be scored as a sign of impairment.

Problems with Field Sobriety Tests

While SFSTs are standardized, they are far from reliable scientific evidence. In fact, even when administered correctly, studies show they are not 100% accurate. Common issues include:

• Environmental factors: Poor lighting, uneven pavement, or bad weather can cause mistakes.

• Physical conditions: Age, weight, or medical conditions (like vertigo or back problems) can mimic impairment.

• Officer error: If the officer does not follow NHTSA guidelines exactly, results may be invalid.

• Nervousness: Many sober drivers perform poorly simply due to stress.

Are Field Sobriety Tests Accurate?

One of the most common questions people ask after a traffic stop is: “Are field sobriety tests accurate in DUI cases?” The answer is: not always. NHTSA claims that when combined, the three SFSTs can predict blood alcohol content (BAC) of 0.08% or higher about 90% of the time. However, that still leaves significant room for error — and that’s when tests are given under ideal conditions.

Can You Refuse Field Sobriety Tests in Colorado?

Unlike chemical testing (breath or blood), Colorado drivers are not legally required to take field sobriety tests. You may politely refuse without facing automatic penalties. However, refusal may increase an officer’s suspicion and could still result in arrest.

Knowing your rights at this stage is critical. A skilled Colorado DUI defense attorney can often argue that the officer lacked probable cause for arrest if field sobriety tests were the main evidence.

After SFST, law enforcement officers will request a test pursuant to

Can You Refuse Field Sobriety Tests in Colorado?

Unlike chemical testing (breath or blood), Colorado drivers are not legally required to take field sobriety tests. You may politely refuse without facing automatic penalties. However, refusal may increase an officer’s suspicion and could still result in arrest.

Knowing your rights at this stage is critical. A skilled Colorado DUI defense attorney can often argue that the officer lacked probable cause for arrest if field sobriety tests were the main evidence.

After SFSTs, police will request chemical testing pursuant to Colorado’s Express Consent Statute. Unlike the field tests, refusal of chemical testing can cause serious issues with driving privileges.

Challenging Field Sobriety Tests in Court

If your case goes to trial, an experienced DUI attorney can challenge field sobriety test evidence in several ways:

• Cross-examining the officer about whether they followed NHTSA procedures.

• Presenting medical records that explain poor performance.

• Showing video evidence that contradicts the officer’s observations.

• Highlighting environmental conditions that interfered with testing.

These strategies often create reasonable doubt, which can make the difference between conviction and dismissal.

The Role of BAC vs. Field Sobriety Tests

Even if you “fail” the roadside exercises, a DUI conviction usually requires chemical test results (breath or blood). However, field sobriety tests are often used to justify arrest and request a chemical test.

This raises another important issue: BAC vs. field sobriety test results. A driver might perform poorly on tests due to medical issues yet blow under the legal limit. Conversely, some drivers with BAC above 0.08% may appear to pass sobriety tests.

Why You Need a DUI Attorney in Colorado

Facing DUI charges can be overwhelming. Police officers and prosecutors often rely heavily on field sobriety test results to justify an arrest. Even when those results are questionable, they can become a key part of the prosecution’s case. Speaking with an experienced Colorado DUI defense lawyer early in the process can make a major difference in the outcome of your case.

At the Lawrence Law Firm, we regularly represent clients in DUI cases across Colorado, including Denver, Aurora, Arapahoe County, Adams County, Douglas County, and Jefferson County.