Reasonable Suspicion for a DUI Stop

Generally, with the exception of DUI checkpoints, police officers are not allowed to stop or detain a driver without cause. The officer must have reasonable suspicion that the driver of the vehicle, or someone in the vehicle, has committed, is committing or will commit a crime. In the case of a DUI, if officers have a reasonable suspicion that drivers are intoxicated, they may pull them over for a brief investigation, which could further lead to field sobriety, breath or other tests.

Signs of Driving Under the Influence

Based on knowledge and experience, police officers look for certain signs that a driver is under the influence, a charge that is referred to in some states as driving while intoxicated. These signs include:

  • Driving noticeably slower than the speed limit or other motorists
  • Erratic driving, such as straddling the center line or drifting between lanes
  • Near misses of other cars or objects close to the road
  • Illegal turns or failure to obey traffic signals
  • Braking frequently or stopping in the middle of the road for no apparent reason

People could also be stopped for infractions that aren't related to their driving behavior, such as a broken headlamp or taillight. Officers could develop reasonable suspicion of DUI or DWI while discussing the infraction with them. If this occurs, an officer may then have the driver perform a field sobriety test or a breath test. If an officer does not have reasonable suspicion that a driver is intoxicated but pulls the vehicle over anyway, any evidence that the driver was impaired could be deemed inadmissible in court.

Reasonable Suspicion vs. Probable Cause

The requirement that police have reasonable suspicion to pull a driver over refers to a specific burden of proof. While officers don't necessarily need hard evidence of a crime, they do need to have knowledge of a certain combination of facts. These must be ones that would lead a reasonable person to suspect that a person is committing, has committed, or is about to commit a crime. An officer who has such a reasonable suspicion generally has the right to briefly stop drivers to question them.

This should not be confused with probable cause, which requires information or evidence that suggests the individual has most likely committed a crime. With reasonable suspicion, detaining the individual for questioning could lead to statements that give the officer probable cause to make an arrest. Refusing to answer an officer's questions cannot create reasonable suspicion.

Getting Stopped Without Reasonable Suspicion

In one limited circumstance, a driver can be stopped and questioned when the officer does not have reasonable suspicion. This is a DUI checkpoint. Typically put in place on holidays and days when drivers are likely to be intoxicated, DUI checkpoints stop cars that pass through in a recurring pattern, such as every third car. In such cases, officers do not need reasonable suspicion in order to stop a driver.

DUI checkpoints are often the subject of controversy as many feel that they break the laws of the Fourth Amendment of the Constitution. However, the Supreme Court has concluded that the need of the state to prevent accidents caused by drunk driving outweighed the minimal intrusion imposed drivers who are stopped.

Getting Help from a DUI Lawyer

If you have been pulled over for a DUI and the officer did not have reasonable suspicion that you have committed a crime, the evidence against you may not be admissible in court. An experienced DUI lawyer could help you to have the evidence thrown out. Additionally, a lawyer could help you form a defense against DUI charges or help you to negotiate a plea deal to reduce your sentence.

The information on this page is meant to provide a general overview of the law. The laws in your state and/or city may deviate significantly from those described here. If you have specific questions related to your situation you should speak with a local attorney.

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