Chicago Criminal Lawyer Blog
Understanding the limits of police authority is critical if you’re facing criminal charges in Chicago or the surrounding counties. The difference between reasonable suspicion and probable cause may seem like legal jargon, but that difference can determine whether the charges against you are legitimate—or completely unconstitutional.
Every day in Cook County courts, we see cases built on street stops, traffic encounters, and so-called “consensual” conversations that evolve into full-blown arrests. The turning point in nearly every case is the justification behind the officer’s decision to approach and search someone. That’s where the legal standards of reasonable suspicion and probable cause come into play.
As criminal defense attorneys in Chicago with decades of courtroom experience, we know how to examine the moment a case truly began: not at the arrest, but at the stop. And we use that to build powerful defenses for our clients.
What Is Reasonable Suspicion and When Can Police Use It?
Reasonable suspicion is a legal threshold that allows officers to stop and briefly detain someone if they believe criminal activity may be taking place. It’s not enough to arrest someone or conduct a full search, but it is enough for temporary questioning or a “stop and frisk” under certain conditions.
The standard was established in Terry v. Ohio and is reflected in Illinois under 725 ILCS 5/107-14. In practical terms, an officer must be able to explain specific reasons for the stop. Vague instincts or profiling don’t qualify.
If you’re walking down Michigan Avenue and an officer approaches you simply because of how you’re dressed or the neighborhood you’re in, that’s not reasonable suspicion. But if they observe you acting in a way that suggests casing a business, exchanging something suspicious in an alley, or visibly concealing an object, that might cross the threshold.
Still, many police officers stop people without documenting those specifics. They may write vague statements like “individual appeared nervous” or “walked away upon seeing officers.” Alone, those don’t meet the standard. And we’ve successfully used that failure to suppress evidence in gun, drug, and theft cases.
Probable Cause: The Legal Basis for Arrests and Searches
Probable cause requires more than suspicion. It means police have enough factual information to reasonably believe that a person has committed a crime. It’s the legal requirement for arrests, search warrants, and certain warrantless searches.
For example, if officers pull over a vehicle in Englewood and smell alcohol, observe slurred speech, and see an open container, they may have probable cause to arrest the driver for DUI under 625 ILCS 5/11-501. If they then see a gun on the seat and the driver doesn’t have a valid FOID or concealed carry license, that’s probable cause for a felony weapons charge under 720 ILCS 5/24-1.6.
Probable cause must be based on facts that can be supported by evidence—witness accounts, observations, recordings, physical objects, etc. If the facts don’t add up or the timeline is inconsistent, we challenge the arrest and seek to suppress evidence gathered as a result.
These Legal Standards Affect Every Criminal Case in Illinois
What begins as a simple stop often escalates—especially in Chicago. Officers may use reasonable suspicion to stop someone for loitering or riding a bike without lights, then claim they smelled cannabis or saw a suspicious bulge, and suddenly that turns into a probable cause arrest.
If they didn’t follow the law at each step, we challenge the stop, the search, and the arrest. We file motions to suppress evidence. And in many cases, once the evidence is excluded, the charges collapse.
These are the kinds of legal tools that most people don’t know how to use. Police count on that. Prosecutors count on defendants not fighting back. That’s why having a defense attorney who knows the law and understands how to apply it in your favor is so important.
Example Case: A Faulty Stop Led to a Dismissal
We represented a young man stopped near a Chicago Transit Authority station late at night. Police claimed he looked like someone “involved in a robbery” but gave no real description. They detained him, asked him questions, and found a pocketknife. He was charged with unlawful use of a weapon.
We obtained bodycam footage showing that officers had no articulable facts—just a vague reference to a call about “suspicious activity.” We argued the stop violated his Fourth Amendment rights and lacked reasonable suspicion. The judge agreed. The knife was excluded from evidence. The case was dismissed.
These outcomes are not rare when you know how to scrutinize a case from the very beginning. It’s about more than whether you had a weapon or substance—it’s about whether police were legally allowed to stop you in the first place.
What You Say and Do Matters After a Stop
After any police stop, how you respond can influence what happens next. But even if you talked to officers, consented to a search, or made a statement, you still have legal rights. A defense attorney can evaluate whether your stop and arrest were lawful and whether your consent was truly voluntary.
Many of our clients believe the case is unwinnable because something illegal was found. But when we trace the case back to the first moment of contact, we often discover constitutional violations that change everything.
Don’t assume your situation is hopeless. If your arrest in Chicago started with a questionable stop or search, let us evaluate your case and explain your options.
What You Should Know If You’re Charged with a Crime in Chicago
Criminal charges in Illinois are prosecuted aggressively, particularly in Cook County. From misdemeanor retail theft (720 ILCS 5/16-25) to felony aggravated battery (720 ILCS 5/12-3.05), the stakes are high. Even a Class A misdemeanor can mean up to 364 days in jail and a permanent criminal record.
After an arrest, your case may proceed to bond court, followed by arraignment, discovery, motion hearings, pretrial conferences, and potentially trial. At every stage, decisions must be made that impact your future.
Without a qualified defense lawyer, you may miss crucial defenses—like challenging reasonable suspicion or probable cause. You may not know when to push for dismissal or when to negotiate a favorable plea. You may not recognize weak evidence or police misconduct. That’s where we come in.
