If police suspect DUI during a traffic stop in the United States, the stop may expand into an impaired-driving investigation. Officers may gather additional observations, ask questions, and look for evidence that could support or eliminate concerns about impairment.
A routine traffic stop can become a DUI investigation if officers observe indicators associated with alcohol or drug impairment.
What happens
During the stop, an officer may:
- Ask questions about alcohol or drug consumption
- Observe speech, coordination, and behavior
- Look for signs such as the smell of alcohol or impaired responses
- Request identification and driving documents
Depending on the circumstances:
- Field sobriety exercises may be requested, including field sobriety tests in the United States used to evaluate possible impairment
- A breath test may be requested where permitted by law when police request a breath test as part of the investigation
- Additional officers may arrive to assist
The driver may be asked to exit the vehicle during the investigation.
The stop may become longer than a typical traffic stop while evidence is gathered.
What determines the outcome
The outcome depends on:
- Officer observations during the stop
- Driving behavior observed before the stop
- Statements made by the driver
- Results of any testing that occurs
- Other evidence available at the scene
Not every DUI investigation results in an arrest.
If officers determine that evidence is insufficient:
- The investigation may end without DUI-related enforcement action
If officers believe sufficient evidence exists:
- The investigation may proceed further
What it may lead to
Common outcome:
- Warning, citation, or conclusion of the stop without DUI charges
Possible escalation:
- Field sobriety testing
- Breath or chemical testing requests
- Extended roadside investigation
Worst realistic outcome:
- A DUI arrest occurs if officers determine sufficient evidence exists to support the arrest
- Vehicle towing or impoundment
- Administrative driver’s license consequences under state law
- Criminal prosecution related to impaired driving
The outcome is usually based on the totality of the evidence rather than a single factor.
Common escalation triggers
- Erratic driving behavior
- Traffic collisions
- Odor of alcohol or drugs
- Open containers or visible evidence inside the vehicle
- Statements suggesting recent alcohol or drug use
What this depends on
Outcomes may vary based on:
- State DUI laws
- Local enforcement practices
- Available evidence during the stop
- Prior DUI-related history
- Whether chemical testing occurs
Procedures and legal consequences differ substantially between jurisdictions.
Who controls the process
DUI investigations are generally conducted by state and local law enforcement agencies.
Criminal charges are handled through the court system, while license-related actions are often handled through state motor vehicle authorities.
Last reviewed: May 2026
This page describes typical operational outcomes. Individual cases vary.