Roadside Tests vs. Post-Arrest Chemical Tests in Colorado: What You Must Know

Getting pulled over for suspected DUI can be confusing—especially when an officer asks you to do tests on the side of the road. Many drivers don’t know which tests are voluntary, which ones are legally required, and what happens if they refuse.

This guide breaks down the key differences between roadside tests and post-arrest chemical tests in Colorado in a clear, simple way, including how the Colorado Express Consent Law affects your obligations after an arrest.

Why This Difference Matters in Colorado DUI Cases

In Colorado, DUI investigations typically happen in two stages:

1. Roadside investigation (before arrest)

2. Chemical testing (after arrest)

The biggest mistake drivers make is assuming all tests are the same. They are not.

Some roadside tests are used to help an officer decide whether they have enough evidence to arrest you. Post-arrest chemical tests, however, are a separate category and can carry serious consequences if refused.

What Are Roadside Tests in Colorado?

Roadside tests are the tests officers may ask you to take during a traffic stop before you are formally arrested.

These tests are typically used to determine whether there is probable cause to arrest you for DUI or DWAI.

Common Types of Roadside Tests

Roadside tests in Colorado usually include:

• Field Sobriety Tests (FSTs)

• Preliminary Breath Test (PBT) (portable breath test)

Let’s break them down.

1) Field Sobriety Tests (FSTs)

Field sobriety tests are physical and coordination-based tests that are performed on the roadside. These tests are designed to check for signs of impairment.

Common Field Sobriety Tests

The most common tests include:

• Walk-and-Turn Test

• One-Leg Stand Test

• Horizontal Gaze Nystagmus (HGN) (eye tracking test)

What Officers Look For

Officers often look for:

• Balance issues

• Difficulty following instructions

• Confusion

• Slurred speech

• Poor coordination

Are Field Sobriety Tests Required?

In most cases, field sobriety tests are voluntary. That means:

• You can refuse them.

• Refusal does not automatically trigger the same penalties as refusing a post-arrest chemical test.

However, refusal can still influence what happens next. An officer may still arrest you if they believe they have enough other evidence.

2) Preliminary Breath Test (PBT) (Portable Breath Test)

A PBT is a small handheld breath device used at the roadside.

What the PBT Does

It provides an estimate of your BAC (blood alcohol concentration). It is mainly used to help the officer decide whether to arrest you.

Is a PBT the Same as a DUI Breathalyzer?

No.

A PBT is not the same as the evidentiary breath test typically given after arrest.

Can You Refuse a PBT?

In many situations, yes. A roadside portable breath test is usually considered a voluntary test during the investigative stage.

But it’s important to understand that refusing a PBT does not mean the DUI investigation ends. The officer may proceed based on:

• Driving behavior

• Odor of alcohol

• Statements you make

• Physical appearance

• Field sobriety test performance (if taken)

What Are Post-Arrest Chemical Tests in Colorado?

Post-arrest chemical tests are tests required after a person is arrested for DUI or DWAI. These are the tests tied to Colorado’s express consent rules.

These Tests Measure:

• Alcohol in your system

• Drugs in your system (in certain cases)

Types of Post-Arrest Chemical Tests

The most common are:

• Breath test (evidentiary breath machine)

• Blood test

• In some cases: urine testing (less common)

When Do Chemical Tests Happen?

Chemical tests typically happen:

• After the officer arrests you, and

• After the officer reads you the express consent advisement

This is a major difference.

Roadside tests are used to help determine whether an arrest should happen. Chemical tests are used after arrest as official evidence.

Key Differences: Roadside Tests vs. Post-Arrest Chemical Tests

Here’s the simplest way to understand it:

Roadside Tests

• Used for investigation

• Often voluntary

• Used to establish probable cause

• Not always strong evidence by themselves

Post-Arrest Chemical Tests

• Required after DUI arrest

• Used as official evidence

• Refusal carries major penalties

• Strong influence on DUI prosecution

Which Tests Can Be Used as Evidence in Court?

This is one of the most important questions.

Field Sobriety Tests

Field sobriety tests can be described in court, and officers may testify about your performance.

But they are subjective.

These tests can also be challenged based on factors like:

• Uneven road surfaces

• Poor lighting

• Weather

• Footwear

• Injury or disability

• Anxiety and stress

PBT Results

PBT results are typically used for probable cause decisions, not as the primary evidence for conviction.

Chemical Test Results (Breath or Blood)

Post-arrest chemical tests are usually the strongest evidence the prosecution relies on.

These results can be used to show:

• BAC level

• Whether you were over the legal limit

• Whether drugs were detected (blood test)

DUI vs. DWAI: Why Testing Matters

Colorado recognizes both:

• DUI (Driving Under the Influence)

• DWAI (Driving While Ability Impaired)

BAC Thresholds (General)

• 0.08% BAC or higher: usually DUI

• 0.05% to 0.079% BAC: often DWAI

Chemical test results play a major role in how the charge is filed and prosecuted.

What Happens If You Refuse a Post-Arrest Chemical Test?

Refusing a chemical test after arrest is a serious decision in Colorado.

Even if you believe refusing will help you avoid a DUI case, refusal often creates a different set of problems—especially with your license.

Potential Consequences of Refusal

Depending on your record and circumstances, refusal can lead to:

• License revocation

• Longer suspension periods than a standard DUI

• Required ignition interlock device

• DMV consequences separate from the criminal case

• Refusal being used against you in court

Colorado treats refusal as a major issue in DUI enforcement.

What If You Cannot Take a Breath Test?

Some drivers cannot complete a breath test due to:

• Medical conditions

• Lung issues

• Physical inability

• Panic or breathing difficulty

In many cases, if breath testing is not possible, law enforcement may request a blood test instead.

Roadside Drug Testing vs. Post-Arrest Drug Testing

DUI investigations in Colorado are not limited to alcohol.

If an officer suspects drug impairment, the process may involve:

Roadside Observations

• Behavior and speech

• Eye appearance

• Coordination

• Drug Recognition Expert (DRE) evaluation (in some cases)

Post-Arrest Testing

• Blood tests are typically used for suspected drug DUI

Unlike alcohol breath tests, drug impairment usually relies more heavily on blood testing and officer observations.

What Drivers Should Know During a Colorado Traffic Stop

This section is about practical awareness. It is not legal advice for a specific case, but it helps drivers understand what’s happening.

1) Stay Calm and Respectful

Escalation rarely helps. Keep your communication clear and controlled.

2) Understand the Two Stages

• Roadside tests = investigation

• Chemical tests = legal evidence after arrest

3) Be Careful With Statements

What you say matters. Officers may ask questions such as:

• “How much have you had to drink?”

• “Where are you coming from?”

• “When did you last drink?”

Your statements can become part of the DUI report.

4) Know That DMV and Criminal Court Are Separate

One of the most misunderstood parts of Colorado DUI law is that:

• The DMV can suspend your license even before your criminal case ends.

That’s why DUI cases often involve both:

• A criminal case, and

• A DMV/license case

Common Myths About DUI Testing in Colorado

Myth 1: “If I refuse everything, I can’t be charged.”

Not true. Officers can arrest you based on other evidence.

Myth 2: “Roadside breath tests and official breath tests are the same.”

Not true. A PBT is different from an evidentiary breath test.

Myth 3: “If I refuse a chemical test, I’m safe.”

Refusal can trigger harsh license penalties and may still be used against you in court.

Myth 4: “Only alcohol triggers DUI testing.”

Not true. Colorado DUI laws also apply to drugs, including prescription medications.

FAQs: Roadside Tests and Chemical Tests in Colorado

Can I refuse field sobriety tests in Colorado?

In most situations, field sobriety tests are voluntary. Refusing them does not automatically trigger express consent penalties.

Can I refuse a roadside portable breath test?

In many cases, yes. A PBT is typically part of the investigative stage and is not the same as a post-arrest chemical test.

Do I have to take a chemical test after a DUI arrest?

Under Colorado’s express consent rules, chemical testing after arrest is treated differently than roadside tests, and refusal can result in serious consequences.

Is a blood test more accurate than a breath test?

Blood tests are often considered more detailed, especially when drug impairment is suspected.

What if I believe the officer did not follow procedure?

Testing procedures, advisements, and timelines can all matter in DUI defense. These issues are often evaluated by a DUI defense attorney.

Conclusion: Know the Difference and Protect Yourself

The difference between roadside tests and post-arrest chemical tests in Colorado is not just technical—it can affect your license, your criminal case, and your future.

To recap:

• Roadside tests are usually investigative and often voluntary.

• Post-arrest chemical tests are tied to Colorado’s express consent rules and carry major penalties for refusal.

• Chemical test results often become the most important evidence in a DUI case.

If you or someone you know is facing DUI charges, understanding how these tests work is one of the first steps in protecting your rights and making informed decisions.