If a police officer suspects that you’re driving over Pennsylvania’s legal BAC limit—0.08 percent—they have the right to detain you for questioning, search for evidence, and make DUI arrests. However, to do so lawfully, they must first establish probable cause. The United States Constitution states that law enforcement must have a certain level of justification before they initiate a traffic stop and subsequent DUI arrest. When these standards aren’t met, you may have legal recourse.
If you’ve been arrested for driving under the influence in Pennsylvania, it’s important that you understand probable cause to determine whether your rights have been infringed upon. We’ve broken down everything you need to know about establishing probable cause in Pennsylvania.
What Does Reasonable Suspicion and Probable Cause Mean in the Context of a DUI Stop?
Before you understand probable cause, it’s important to understand the concept of “reasonable suspicion.” This initial stop often leads to a DUI investigation where officers gather evidence to establish probable cause. A police officer can detain a person for questioning, search for evidence, and make a DUI arrest in Pennsylvania if they establish both reasonable suspicion and probable cause. Although these two terms are sometimes used interchangeably, there are several key differences.
Reasonable Suspicion in DUI Cases
In Pennsylvania, law enforcement must have a reasonable suspicion that a person has violated the law in order to lawfully pull them over for driving under the influence. This means that an officer has reason to believe—based on their training and experience—that a crime has been committed, is being committed, or will be committed, justifying traffic stops.
While reasonable suspicion is subjective in nature, law enforcement officials must have more than a hunch or gut feeling to detain someone. Certain facts and circumstances must be apparent. For example, if an officer notices that a driver commits a traffic violation or is otherwise driving erratically, the officer has reasonable suspicion that the driver is intoxicated and can pull the person over.
Definition of Probable Cause
Probable cause is a legal standard that governs when law enforcement officers can make an arrest, conduct a search, or obtain a warrant. It is a higher threshold than reasonable suspicion and requires a reasonable belief, based on factual evidence, that a person has committed, is committing, or is about to commit a crime. In the context of DUI cases, probable cause is essential for the initial stop, arrest, and collection of evidence. This means that before a police officer can lawfully arrest someone for a DUI, they must have concrete evidence suggesting that the driver is impaired. This evidence can come from various observations and tests conducted during the traffic stop.
Probable Cause in DUI Cases
While reasonable suspicion allows an officer to stop and detain a motorist temporarily, an officer must meet a higher standard of “DUI arrest probable cause” before obtaining a warrant, searching a vehicle, or arresting a suspected drunk driver. In general, a DUI arrest probable cause requires facts that demonstrate a high probability that the driver is impaired or has consumed alcohol in excess of the legal limit. Visual findings, like a driver’s mannerisms, speech, or behavior, can be enough to meet probable cause standards. A police officer may also establish probable cause by other means, including the smell of alcohol or open containers in the car.
The main difference between reasonable suspicion and probable cause is that the former exists if a reasonable officer suspects criminal activity, while the latter exists if it can be assumed that a reasonable individual who’s not a police officer would suspect a crime based on the actions of the suspect.
One common tool that Pennsylvania law enforcement uses to establish probable cause is a breathalyzer. These devices are used to estimate blood alcohol content (BAC) from a breath sample. Another go-to technique that police often utilize to establish probable cause after a DUI stop is field sobriety testing. This brief examination typically involves a one-leg stand, horizontal gaze nystagmus, and a walk-and-turn in Pennsylvania.
It’s important to note that if the police fail to identify facts that lead to probable cause, any evidence gathered from that point on may not be admissible in court. This may lead to a dismissal in some cases. If you think this may be the case, it’s vital that you get in touch with an expert Montgomery County DUI defense lawyer who may be able to help you reduce or eliminate the penalties associated with a conviction.
Factors That Contribute to Probable Cause
Several factors can contribute to establishing probable cause in a DUI case. These factors are often observed during the initial traffic stop and subsequent interactions with the driver. Understanding these factors can help you recognize what constitutes probable cause and how it can impact your DUI case.
Driving Behavior
One of the first indicators that can lead to a DUI stop is the driver’s behavior on the road. Erratic driving, such as weaving between lanes, sudden stops, or driving significantly below the speed limit, can raise suspicion. Police officers are trained to recognize these behaviors as potential signs of impaired driving. When an officer observes such driving behavior, it can provide the reasonable suspicion needed to initiate a traffic stop.
Physical and Behavioral Indicators
During the traffic stop, the officer will look for signs such as slurred speech, red or watery eyes, and the smell of alcohol. They may also note if you have difficulty retrieving your driver’s license or registration or if you appear confused or disoriented. These physical and behavioral indicators can contribute to establishing probable cause for a DUI arrest. For instance, if an officer notices slurred speech or the smell of alcohol, these observations can strengthen the case for probable cause.
Police Officer’s Observations
The officer’s observations during the traffic stop play a significant role in building the case for probable cause. They will document their interactions with you, noting any signs of impairment such as slurred speech, unsteady movements, or the smell of alcohol. The officer’s observations can provide critical evidence in establishing probable cause for a DUI arrest. In addition to these factors, other evidence such as field sobriety test results, breathalyzer or blood test results, and witness statements can also contribute to establishing probable cause. A skilled DUI defense attorney can challenge the probable cause for a DUI arrest and argue that the evidence obtained was not sufficient to establish probable cause.
By understanding these factors, you can better navigate the complexities of DUI investigations and protect your rights throughout the legal process.
Contact an Experienced DUI Defense Lawyer in Montgomery County
If you were charged with a DUI and think that an officer might not have met probable cause or reasonable suspicion requirements, we invite you to contact us for a free consultation. At Rubin, Glickman, Steinberg & Gifford, we understand how challenging this time can be for you, which is why we’re dedicated to fighting for your rights and protecting your interests throughout the legal process. Our highly trusted and well-versed legal team understands the ins and outs of Montgomery County DUI defense law and will be with you every step of the way.
For more than 65 years, the attorneys at Rubin, Glickman, Steinberg & Gifford have been serving the legal needs of clients in Montgomery County, Bucks County, Lehigh County, Chester County, Delaware County, and throughout the surrounding areas. We’ve earned the trust and respect of clients facing a wide range of legal problems. Our attorneys are ready to protect you and guard your rights. Call (215) 822-7575 or complete our online contact form today.
Rubin, Glickman, Steinberg & Gifford P.C.
Pennsylvania Attorney's
April 8, 2025
