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How Police Officers Determine Probable Cause for DUI Arrests


Do you want to learn how police officers determine probable cause for DUI arrests? Contact Christopher J. Mutimer of Scrofano Law PC for more information.

What Is the Importance of Probable Cause in a DUI Traffic Stop?


A police officer may stop a driver for committing a traffic violation while driving. However, sometimes officers make traffic stops without a lawful reason.

A traffic stop can be a nerve-racking experience. You may feel even more anxious or puzzled when stopped without a lawful reason. Remember, through its Fourth Amendment, the United States Constitution prohibits unreasonable searches and seizures. Pulling over and searching an individual without a valid reason is a violation of their rights.

Read on to understand what is meant by reasonable suspicion and probable cause. The presence or absence of these essential elements can be the differentiating factor between a lawful traffic stop and an unlawful one. Thus, a proper understanding of these concepts is critical.


Meaning and Its Importance

A probable cause exists when:

  1. Certain facts and circumstances are available to a police officer when making an arrest.
  2. These facts and information possessed by the police officer would cause a reasonably cautious person to assume that a crime has been committed.

It is unlawful for an officer to make a traffic stop or DUI arrest without probable cause. Additionally, any unlawfully obtained evidence may be inadmissible in court.

For example, driving under the influence (DUI) is considered a criminal offense with life-changing consequences. However, an illegal traffic stop serves as a defense against the prosecution’s evidence against you.

What Kind of Behaviors Give Rise to a Reasonable Suspicion?


An officer should not make a DUI arrest solely based on hunches. They must be able to show the facts that led to them having suspicions about the driver’s behavior. Generally, reasonable suspicion is a lower standard than probable cause.

Several behaviors may be used to establish reasonable suspicion, including:

  • Drifting

  • Driving erratically

  • Driving in between lanes

  • Driving too slowly

  • Driving at high speed

  • Driving without a headlight

  • Driving without a license plate

  • Driving through red lights

  • Stopping a vehicle for no treason

  • Swerving

  • Weaving

What Behaviors Establish Probable Cause in DUI Investigations?


After making the traffic stop, the officers will search for signs of intoxication. The following behaviors can serve as evidence to establish probable cause:

  • Bloodshot or watery eyes: Drinking large amounts of alcohol may cause redness in the eyes. Officers often cite bloodshot eyes as a sign of intoxication. However, other factors, such as allergies or crying, may lead to redness.
  • The smell of alcohol on a motorist’s breath: Law enforcement officers usually pay attention to the driver’s breath. However, it is not a very reliable sign.
  • Slurred speech: High levels of intoxication can lead to slurred speech. Other reasons for slurred speech may include a brain tumor, stroke, or migraine. An officer unfamiliar with their voice will be unaware of how they speak.
  • Verbal admission of intoxication: Verbal admissions can damage the chances of avoiding a DUI conviction. It is important to speak to a lawyer before admitting to consuming alcohol.
  • Failed field sobriety tests (FSTs): Failing field sobriety DUI testing, such as the one-leg stand or walk-and-turn, may show signs of intoxication. A skilled attorney can prove the inaccuracy of these tests by considering other factors.
  • Failed breathalyzer test: Breathalyzer readings measure the driver’s blood alcohol level. Failed readings indicate that the driver is above the legal limit. However, these readings can be inaccurate due to faulty breath machines.

Some DUI arrests occur after a law enforcement officer discovers these signs at an accident scene. The prosecution may use such signs as evidence in court to prove that the driver was drunk driving.

When Is a Traffic Stop Lawful in DUI Cases?


DUI investigations often begin after a traffic stop. But, all traffic stops do not require reasonable suspicion. Some circumstances that may present an officer with a chance to conduct an investigation include:

  1. Traffic violations: Generally, all traffic violations justify a traffic stop. A police officer can lawfully stop your vehicle after you violate a traffic law.
  2. Checkpoints: Law enforcement sets up roadblocks to enforce DUI laws. Officers will search for signs of intoxication before letting a driver off. They may conduct a field sobriety test if they notice any sign of impairment.
  3. Traffic accidents: Vehicle collisions create an opportunity for DUI investigations. An officer who notices signs of intoxication at the accident scene will conduct a DUI investigation.
  4. Welfare checks: Officers may conduct a welfare check after noticing a parked vehicle. Physical control of a vehicle includes sitting in the driver’s seat. Further, officers may investigate a vehicle if they believe someone is in danger.
  5. Reasonable suspicion: Officers may stop a vehicle to investigate suspicious behaviors. They may also receive a tip for criminal behavior. For example, driving a stolen vehicle or kidnapping.


What to Do if You Are Arrested Without Probable Cause


Individuals arrested and taken to the police station may do the following:

  1. According to the Fifth Amendment, individuals have a right to remain silent. You can refuse to share information with the police.
  2. Remain calm and resist arguing with the police officer.
  3. Consider hiring a professional lawyer such as Christopher J. Mutimer of Scrofano Law PC.
  4. Protect all the evidence you collected, including photo and video evidence.
  5. Follow all lawful directions of the police but do not admit to any offenses.
  6. Request for the names and information of the arresting officers.
  7. Provide your name and address to the police officer.
  8. Inform your lawyer of all evidence and witnesses from the traffic stop.

How Can a DUI Lawyer Help You?


Contact Christopher J. Mutimer of Scrofano Law PC if you think you were unlawfully stopped without probable cause. We can explain your rights and make recommendations for your next move.

  • We can assist in filing a motion to suppress evidence that violates your Fourth Amendment rights.

  • We are trained in DUI defense and know how to challenge evidence obtained from a DUI stop.

  • We can obtain a copy of the police report and examine all claims of intoxication.

  • We understand the relationship between a misdemeanor DUI and employment and can fight to reduce your charges.

We have handled various DUI cases in Washington, D.C., and have extensive trial experience. We can provide you with professional legal representation and navigate your case the right way. Contact us today!


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