For police to lawfully arrest you for DUI in Nevada, they must have probable cause that you are driving under the influence. This means that a reasonable and cautious police officer would have a rational basis to believe that you drove:

• while drunk or high, or
• with a blood alcohol concentration (BAC) of .08% or higher.

If we can show the officers in your case lacked sufficient probable cause to arrest you, the prosecutors may agree to dismiss your case due to police misconduct. This is true even if you were technically under the influence at the time.

To help you better understand probable cause, our Las Vegas DUI lawyers will answer the following questions:

• 1. When can police pull me over?
• 2. When can police start a DUI investigation?
• 3. What builds probable cause?
• 4. How do I challenge probable cause?
• Additional Reading

1. When can police pull me over?

Police may pull you over in Nevada when they have reasonable suspicion, which is a lower standard than probable cause.

Reasonable suspicion is when there are specific facts that would lead an officer to suspect you are committing or have committed a traffic infraction or crime, whether related to drunk driving or not. In fact, many DUI arrests stem from traffic stops for non-DUI reasons such as expired tags or broken taillights.

The only exception to the reasonable suspicion requirement is DUI checkpoints, which is where every driver going through the checkpoint gets stopped. The U.S. Supreme Court has held that sobriety checkpoints do not violate the Fourth Amendment as long as they conform to certain standards of fairness and objectivity.¹

2. When can police start a DUI investigation?

Once police pull you over, they may proceed with a DUI investigation if they have reasonable suspicion that you may be under the influence. Typical signs are:

• an erratic driving pattern (such as weaving, swerving, driving too slowly, making wide turns, and other traffic violations);
• you fumble when producing your license and registration;
• your speech is slurred;
• you admit that you have been drinking or came from a bar;
• there are drugs, drug paraphernalia or alcohol visible inside your car; and/or
• you exhibit physical symptoms of inebriation (such as bloodshot, glassy eyes and the odor of alcohol or marijuana).

For example, simply having a lapsed registration or no insurance should not give the officer reasonable suspicion you may be impaired. You have to display some kind of behavior that indicates impairment.

The DUI Investigation

If an officer reasonably suspects you are a drunk driver (or drugged driver), they may detain you for an investigation. In Nevada, this typically involves:

• questions about where you have been and whether you have been drinking or using drugs;
• a preliminary breath test (PBT) on a handheld breathalyzer;
• one or more field sobriety tests (FSTs); and/or
• a search of your vehicle (if you consent, which we do not recommend).

With each phase of the DUI– the stop, the investigation and then a possible arrest—there is a higher standard for proceeding.

3. What builds probable cause?

In Nevada, your arresting officer must be able to articulate the exact facts that led them to have probable cause that you were driving under the influence. Examples include:

• you failed the preliminary breath test;
• you failed one or more of the field sobriety tests; and/or
• drugs or alcohol were in your car.

The officer will not necessarily explain to you at the time of your arrest the basis for their probable cause. However, it should be contained in the police report.⁶

4. How do I challenge probable cause?

Here at Las Vegas Defense Group, we have represented literally thousands of people charged with driving under the influence of drugs or alcohol. In our experience, the following six arguments have proven very effective at showing the police lacked probable cause to make a DUI arrest:

1. You were pulled over for an unlawful reason (such as your race).
2. You did not display any signs of intoxication.
3. You passed the preliminary breath test.
4. You passed the field sobriety tests.
5. There are obvious, non-alcohol-related reasons to explain your intoxicated-like behavior, such as being tired or nervous.
6. The police search of your car was unconstitutional.

Motions to Suppress

If the police pulled you over or began to investigate you for DUI without “reasonable suspicion” – or if they arrested you without “probable cause” –  we would file a motion asking the court to suppress (disregard) any evidence the police obtained. The logic is that since the original stop, investigation, or arrest was illegal, so too is any evidence the police then found.

If the court agrees and suppresses the state’s evidence (which may even include failing blood test or breath test results), the prosecution could be left with too weak a case to continue prosecuting. They may then agree to drop your charge or reduce it to a lesser charge as part of a plea bargain.

In practice, Nevada judges are reluctant to suppress evidence for lack of probable cause in DUI cases. However, it often makes sense to file a motion anyway. As Las Vegas DUI defense lawyer Michael Becker explains:

“A motion to suppress evidence presents an opportunity to cross-examine your arresting officer. We can often discover weaknesses in the district attorney’s case and use them to negotiate reduced charges or even get them dismissed outright.”

Additional Reading

For more in-depth information, refer to these scholarly articles:

• Probable Cause, Probability, and Hindsight – Journal of Empirical Legal Studies
• Putting Probability Back into Probable Cause – Texas Law Review
• Probabilities in Probable Cause and Beyond: Statistical Versus Concrete Harms – Law and Contemporary Problems
• Probable Cause Pluralism – Yale Law Journal article on the complexities of the probable cause standard.
• Probable Cause Revisited – Stanford Law Review article discerning how probable cause operates.

Legal References: