Driving under the influence investigations in Utah follow a structured three-phase process that law enforcement officers are trained to use. Understanding these phases can help drivers know how DUI investigations develop and what legal defenses may exist.
Every Utah DUI investigation typically includes the following stages:
- Vehicle in Motion
- Personal Contact
- Pre-Arrest Screening
Each stage provides the officer with opportunities to observe potential signs of impairment. However, these same stages also provide legal opportunities for defense attorneys to challenge the investigation.
Phase 1: Vehicle in Motion
The Vehicle in Motion phase begins before the officer ever speaks to the driver. During this stage, the officer observes the vehicle’s driving behavior to determine whether there is a legal reason to initiate a traffic stop.
Common Reasons for a DUI Traffic Stop in Utah
Police officers must have reasonable suspicion to stop a vehicle. In Utah, there are many possible legal reasons for a stop under the traffic code, including:
- Broken headlights or taillights
- Cracked windshield
- Expired registration
- Speeding or traffic violations
- Unsafe lane changes
- Failure to signal
- Vehicle equipment violations
- Visible vehicle damage
Utah’s traffic laws are extensive. Under Utah Code Title 41-6a, there are dozens of provisions that allow officers to legally initiate a stop.
Once the officer begins following the vehicle, dash camera footage typically records the driving pattern. Officers may evaluate factors such as:
- Lane position
- Speed consistency
- Delayed response to emergency lights
- How safely the driver pulls over
- Whether the vehicle parks straight or erratically
Legal Challenges to the Vehicle Stop
The vehicle in motion phase is one of the most important points for a DUI defense attorney. If the officer did not have reasonable suspicion to pull the vehicle over, the stop may be considered unconstitutional under the Fourth Amendment.
Defense attorneys may file a motion to suppress evidence, arguing the stop was illegal.
However, these motions can be difficult to win because courts often defer to the officer’s observations. Still, when successful, suppression motions can result in dismissal of the DUI charges.
Phase 2: Personal Contact
The personal contact phase begins when the officer approaches the driver after the vehicle has been stopped.
During this stage, the officer is trained to observe physical and behavioral indicators of impairment.
What Officers Look for During Personal Contact
Experienced DUI officers pay attention to many small details, including:
- Bloodshot or watery eyes
- Slurred speech
- Odor of alcohol
- Slow or confused responses
- Difficulty locating license or registration
- Droopy eyelids or lack of coordination
Officers may also evaluate how well the driver performs divided attention tasks, such as:
- Listening to instructions
- Answering questions
- Locating documents
- Following multiple directions
These actions help the officer decide whether to continue the investigation into the pre-arrest screening phase.
Phase 3: Pre-Arrest Screening
The pre-arrest screening phase is where the officer attempts to gather enough evidence to determine whether probable cause exists to arrest the driver for DUI.
This stage typically includes field sobriety tests and preliminary breath testing.
Standardized Field Sobriety Tests (SFSTs)
Common standardized field sobriety tests include:
- Horizontal Gaze Nystagmus (HGN) – eye movement test
- Walk-and-Turn Test
- One-Leg Stand Test
These tests are designed to evaluate balance, coordination, and divided attention.
However, the tests must be administered according to strict standardized procedures.
If the officer performs them incorrectly, the results may be challenged in court.
Portable Breath Tests
Officers may also request a portable breath test (PBT) using a handheld device at the roadside.
As of March 2026, in Utah:
- Field sobriety tests are voluntary
- Portable breath tests are voluntary
Drivers may decline these roadside tests.
However, once an officer arrests a driver for DUI, refusing an official chemical test (breath or blood) can result in license suspension and additional legal consequences under Utah’s implied consent law.
Legal Defenses in Utah DUI Investigations
Each phase of a DUI investigation creates potential areas for legal defense.
Challenging the Traffic Stop
If the officer lacked reasonable suspicion, the defense may argue the stop violated constitutional protections against unlawful search and seizure.
Challenging Field Sobriety Testing
Field sobriety tests can be challenged if:
- Instructions were unclear
- The tests were administered incorrectly
- Environmental factors affected performance
- Medical conditions impacted balance or coordination
Improperly conducted tests may weaken the officer’s probable cause to arrest.
Challenging Probable Cause
If the officer lacked sufficient evidence to justify the arrest, the defense may file motions seeking dismissal.
Because DUI cases rely heavily on officer observations and procedure, small mistakes in the investigation can become important legal issues.
Why Hiring a Utah DUI Attorney Matters
DUI cases often involve technical legal issues and procedural rules.
An experienced DUI attorney can:
- Review dash camera and body camera footage
- Analyze whether the traffic stop was lawful
- Examine field sobriety testing procedures
- File motions to suppress evidence
- Challenge probable cause for arrest
Because DUI charges can carry serious consequences, including fines, license suspension, and possible jail time, legal representation is critical.
If field sobriety tests were administered incorrectly or if the stop was unlawful, it may be possible to seek dismissal or reduction of the charges.
Frequently Asked Questions About Utah DUI Investigations
What are the three phases of a Utah DUI investigation?
The three phases are vehicle in motion, personal contact, and pre-arrest screening. Officers use these stages to gather evidence before making a DUI arrest.
Can police stop a vehicle without a reason in Utah?
No. Officers must have reasonable suspicion that a traffic violation or criminal activity occurred before initiating a stop.
Are field sobriety tests mandatory in Utah?
No. As of 2026, field sobriety tests are voluntary in Utah.
Is the roadside breath test mandatory?
Portable roadside breath tests are generally optional, but refusing an official chemical test after arrest can result in license suspension.
Can a DUI case be dismissed because of an illegal stop?
Yes. If the stop is ruled unconstitutional, a judge may suppress evidence, which can lead to dismissal.
Why do officers ask for license and registration during a DUI stop?
This helps officers evaluate coordination, memory, and divided attention, which may indicate impairment.
Speak With an Experienced Utah DUI Attorney
If you are facing DUI charges, understanding how Utah DUI investigations work is an important first step in protecting your rights.
Each phase of the investigation may provide opportunities for legal challenges.
Call or Text Utah DUI Attorney Jake Gunter to discuss your case and learn about possible defenses.