What is Probable Cause?

If a police officer stops you, searches your car, or places you under arrest, they cannot do so on instinct alone. The law requires them to meet a specific legal threshold called probable cause, and it is one of the most important constitutional protections you have. When law enforcement fails to meet that standard, the evidence they gather may not be usable against you in court, and in some cases the charges themselves may not survive.

At Bruno Lilly LeClere, PLLC, our criminal defense attorneys build a significant number of defenses around exactly this issue. Founding attorney Havilah Louise Bruno Lilly spent years as a Deputy District Attorney before switching to defense work, which means she understands how law enforcement establishes probable cause, where that justification breaks down, and how to challenge it effectively in court.

What Is Probable Cause?

Probable cause is the legal standard law enforcement must meet before making an arrest, conducting a search, or obtaining a warrant. As defined by the Cornell Law Legal Information Institute, probable cause exists when the facts and circumstances within an officer’s knowledge would lead a reasonable person to believe that a crime has been committed or that evidence of a crime is present in the location to be searched.

The Fourth Amendment to the U.S. Constitution, along with Article II, Section 7 of the Colorado Constitution, both protect against unreasonable searches and seizures. Probable cause is the threshold that separates lawful police action from a constitutional violation. It is well above a hunch or gut feeling, but substantially below the “beyond a reasonable doubt” standard required to convict someone at trial.

Probable Cause vs. Reasonable Suspicion

These two standards are related but serve different purposes, and confusing them is one of the most common mistakes people make when evaluating whether their rights were violated.

Reasonable suspicion is a lower threshold that allows an officer to briefly detain you or conduct a limited pat-down if they can point to specific, articulable facts suggesting criminal activity may be occurring. A minor traffic violation — a broken taillight, failure to signal, rolling a stop sign — is enough to justify a traffic stop under reasonable suspicion. Probable cause is a higher standard required for more intrusive actions like a full arrest, a search of your home, or a vehicle search beyond a plain-view observation. If an officer escalates from a stop to a search or arrest without crossing from reasonable suspicion into probable cause, that escalation may be unconstitutional.

Probable Cause for Traffic Stops and Vehicle Searches

Our Greeley DUI attorneys frequently handle cases that begin with a traffic stop. Officers need only reasonable suspicion to pull you over, but they need probable cause to search your vehicle. There are several ways probable cause for a vehicle search can be established:

• Contraband or evidence of a crime in plain view inside the vehicle
• The odor of alcohol or marijuana detected by the officer during the stop
• Statements made by the driver or passengers that suggest criminal activity
• A positive alert from a drug detection dog, with one important caveat

Colorado has a specific rule on drug detection dogs worth knowing. Because marijuana is legal to possess in Colorado, a dog trained to alert to marijuana cannot be used to establish probable cause for a vehicle search without additional evidence. If the dog alerts and marijuana possession alone is the basis for the search, that search may be unconstitutional under Colorado law. This is a detail that matters in drug crime cases and is one that officers do not always get right.

Probable Cause for Arrests

An arrest requires probable cause regardless of whether it is made with or without a warrant. The determination is based on the totality of the circumstances known to the officer at the moment of arrest. If an officer witnesses a crime directly, that generally satisfies probable cause. If they are acting on information from a witness or informant, the reliability and specificity of that information matters significantly.

If you are arrested without a warrant in Colorado, you have the right to a prompt probable cause determination by a judge. This hearing must occur within 48 hours of your arrest. If the court finds that probable cause did not exist, you may be entitled to release and any evidence gathered as a result of the unlawful arrest may be suppressed.

Home Searches and Search Warrants

Your home receives the strongest constitutional protection of any space. Police generally must obtain a search warrant supported by probable cause before entering and searching your residence. To get that warrant, an officer must submit an affidavit to a judge laying out the specific facts that establish probable cause. The judge independently reviews that affidavit and either issues or denies the warrant.

There are exceptions — exigent circumstances such as hot pursuit of a fleeing suspect, the risk of imminent harm, or the likelihood that evidence is about to be destroyed can justify a warrantless entry. But these exceptions are narrow and are frequently challenged in court. If police entered your home without a warrant and the circumstances do not fit a recognized exception, your attorney may have strong grounds for a suppression motion.

What Happens When Probable Cause Is Challenged

When an arrest or search was conducted without proper probable cause, your Greeley criminal defense attorney can file a motion to suppress the evidence obtained. This is one of the most powerful tools in criminal defense. Under the exclusionary rule, evidence gathered in violation of your constitutional rights generally cannot be used against you at trial. If the prosecution’s key evidence gets suppressed, they may not have enough remaining to sustain the charges.

Common situations where probable cause challenges succeed include traffic stops that escalated without proper justification, searches based on unreliable informant tips that were not independently corroborated, arrests based on misidentification or mistaken facts, and drug dog alerts on vehicles in cases where the dog was trained to detect marijuana.

Frequently Asked Questions

Contact Bruno Lilly LeClere, PLLC for a Free Consultation

Probable cause challenges are among the most technical and effective defenses available in Colorado criminal law. They require an attorney who knows how to identify unconstitutional police conduct, file the right motions before court deadlines pass, and argue those motions persuasively in front of a judge. Founding attorney Havilah Louise Bruno Lilly spent years on the prosecution side of these arguments before building a firm dedicated to the defense. With offices in Greeley, Fort Collins, and Mead, our team represents clients facing criminal charges throughout Weld, Larimer, and Boulder Counties.

If you believe your rights were violated during an arrest or search, time matters. Contact us before your next court date. Reach out online today for a free, completely confidential consultation.

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