Everything You Need To Know About Probable Cause For A DUI Stop

What Is Probable Cause?

In order to detain and arrest someone for a DUI, a law enforcement officer must have probable cause. Attorney Diana Aizman explains probable cause as:

A reasonable belief  that a crime has been or is being committed.

The officer must be able to specifically articulate the reasons for this belief—a “hunch” is not enough.  There are three stages of probable cause required in the DUI process and each stage requires more proof and articulation than the last.

  • Reasonable Suspicion
  • Articulate Why The Officer Suspects A Crime
  • Establish Probable Cause For Arrest

1. Reasonable Suspicion

Unreasonable search and seizure is prohibited under the Fourth Amendment of the United States Constitution.1 This means that an officer must have reasonable suspicion that a crime is taking place before he is permitted to pull over your vehicle for a traffic stop.

Any traffic violation is enough for a police officer to pull you over.  Suspicion of driving under the influence is not necessary in order for the officer to stop you. The only exception to this rule is a sobriety checkpoint, which is an administrative procedure that has its own strict rules and guidelines2.

2. Articlute Why The Officer Suspects You

After you are pulled over, the law enforcement officer must have probable cause in order to begin a DUI investigation. Before an officer can start asking you questions about drinking he must be able to articulate why he suspects you of driving under the influence.  If the officer observes signs of intoxication, this is likely enough to establish probable cause for a DUI case3.  Some of these observations include:

  • Alcohol in the car, whether opened or unopened
  • The smell of alcohol on your breath or in the vehicle
  • Red, watery, or glassy eyes
  • Slurred speech
  • Disorientation, or fumbling

This is usually sufficient to establish enough probable cause for the officer to ask more in depth questions about driving under the influence.

3. Establish Probable Cause For An Arrest

Finally, probable cause is also required before the officer can make an arrest for a DUI.  For this, the officer must be able to establish exactly why he someone was arrested for a DUI.  This is the highest level of probable cause required because with it come severe consequences.  Some examples of probable cause include:

California has an implied consent law and after a DUI arrest, you have to submit to a

If at any point before, during, or after your arrest, the officer cannot establish to the court that there was probable cause to continue to the next phase of the investigation, your attorney should attempt to have the evidence suppressed in a 1538.5 Suppression Hearing4.  If your evidence is not suppressed, it is still a good opportunity for the lawyer to cross examine the officer and discover weaknesses in the prosecution’s case in order to get your charges dismissed or reduced later on in the proceedings.

Probable Cause FAQs

What exactly is a section 1538.5 Suppression Hearing?

When your attorney believes that the arresting officer did not have probable cause that you were driving under the influence, he or she can file a motion to suppress with the court.  This is a request to get all evidence that was obtained after there was no probable cause to be tossed out.  If the court grants this motion at the suppression hearing, your case may be dismissed for lack of evidence. If there is still other evidence against you that has not been suppressed, the prosecution may still move forward on your case but it will be weaker with the lack of evidence.

Do the police have to read me my Miranda rights when they arrest me?

Many people believe that it is a harmful mistake if a police officer does not read you your Miranda rights after you have been arrested.  This is a common misconception. An officer only has to read you your rights if two things happen: (1) you are lawfully placed under arrest, and (2) you are subjected to custodial interrogation. Custodial interrogation occurs when the officer asks you questions after your lawful arrest from which your answers could incriminate you and be used against you in your hearing.

What is the difference between probable cause and reasonable suspicion?

Probable cause is a stricter standard than reasonable suspicion.  However, it is common throughout court proceedings that the two phrases are used interchangeably.

Is my refusal to take a preliminary alcohol screening or to submit to the field sobriety test enough for probable cause?

Refusal of either a of these tests alone is not enough to for the officer to establish probable cause that you were driving under the influence.  However, it is important to remember that there may be other symptoms or signs that the officer articulates as his probable cause even without the field and breath tests.

Additional Issues To Consider

DUI Checkpoints

Law enforcement officers are required to follow very strict rules at a sobriety checkpoint. Sobriety checkpoints are legal in nature but the specific checkpoint that you were arrested at may have some mistakes that will be create a strong defense and encourage the prosecution to reduce or dismiss your charges completely.

Police Mistakes

The probable cause requirement for a strong DUI case is one of the many areas in which a law enforcement officer can make a mistake in a dui case that can negatively affect the case against you.  A non-exhaustive list of errors include:

Next Steps

If you have been arrested and would like to learn more about what attorneys charge.

If you want to understand why its important to have an attorney represent you.

If you are ready to discuss a pending case with an attorney contact the Aizman Law Firm at 818-351-9555 for a free confidential consultation.

Get Legal Help Now

Request A Free Consultation 818-351-9555 


  1. Constitution of the United States, Amendment Four []
  2. Ingersoll v. Palmer, 43 Cal.3d 1321 (1987 []
  3. Terry v. Ohio, 392 U.S. 1 (1968 []
  4. Cal. Penal Code section 1538.5(a)(1)(A []

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