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Probable Cause To Stop Vehicle | Chicago DUI Lawyer

Illinois DUI Lawyers know that for your stop and DUI arrest to be justified under the law, the officer must be able to show that he had reasonable suspicion of a violation. In most cases, this requires that the officer personally observe a traffic violation of some sort before he stops you. (In some cases, which your Chicago DUI Attorney will look at later, a tip based on someone else's observations of a violation could justify a stop.)
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Probable Cause To Stop Vehicle

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Chicago DUI Attorney: No Probable Cause to Arrest You 

If you've been arrested on a stop and charged with DUI, you're facing a whole host of negative consequences that could completely change your life. But an experienced Chicago DUI Attorney might help you find a good basis for having the officer's stop of you and your consequent arrest thrown out of court. Your knowledgeable Illinois DUI Lawyer will have at his command a whole body of case law that states when an officer has gone too far and has violated your constitutional rights.

Did the Officer who Arrested You have a Reasonable Suspicion of a DUI violation?

Illinois DUI Lawyers know that for your stop and DUI arrest to be justified under the law, the officer must be able to show that he had reasonable suspicion of a violation. In most cases, this requires that the officer personally observe a traffic violation of some sort before he stops you. (In some cases, which your Chicago DUI Attorney will look at later, a tip based on someone else's observations of a violation could justify a stop.)

The U.S. Supreme Court has specifically found, in Delaware v. Prouse, 440 U.S. 648, 663 (1979), that an officer who stops you just to conduct a license and registration check, or because he had nothing more urgent to do at the time, does not have a reasonable suspicion for stopping you and therefore has violated your rights under the 4th Amendment of the U.S. Constitution. Where your rights have been so violated, the charge against you is invalid and your case could be tossed out of court.

Chicago DUI Attorney notes: To stop you, the police officer must have an "articulable and reasonable" suspicion of unlawful activity on your part, like Driving Under the Influence of alcohol. To arrest you, the officer must have probable cause.

The police officer out on the job must sometimes determine whether there's reasonable suspicion for a stop in just seconds. Your Illinois DUI Lawyer has much more time to later review the events and determine whether reasonable suspicion actually existed under the law. Because of the short time frame in which officers must decide to stop or not to stop, they sometimes make mistakes. A good Chicago DUI Attorney could turn those mistakes to your advantage to request dismissal of the case against you.

Practiced Illinois DUI Lawyers realize that any real traffic violation could lead to your stop by police. And Chicago DUI Attorneys know that once you're stopped, the officer can arrest you if probable cause exists. Some of the violations that could lead to an officer stopping you include:

  • Speeding
  • Driving too slowly (which can also be dangerous to other motorists)
  • Weaving on the road
  • Failing to stop at a red light or a stop sign
  • Failure  to signal a turn
  • Vehicle equipment defects such as a broken taillight or a missing or obscured license plate

An Illinois DUI Lawyer knows that once the police have validly stopped you for a simple traffic violation, the officer could validly arrest you on other charges. This Chicago DUI Attorney emphasizes that you could be charged with DUI or drug possession if the officer finds evidence of it, even if your stop was on the pretext of a broken taillight.

Historically, there has been some controversy over what constitutes "reasonable suspicion" for a traffic stop, which has led to some diligent study by Illinois DUI Lawyers. The specific facts and circumstances of your individual case will determine whether your Illinois DUI Lawyer has a solid basis for getting your stop and arrest overturned. It's important that you hire a skilled Chicago DUI Attorney for your case as soon as possible after your arrest before any evidence or facts that might work in your favor have been forgotten or lost.

Was Your Stop and Arrest made on the Basis of a Tip given to the Police?

This Chicago DUI Attorney notes that whether a stop based upon a tip made to the police was lawful revolves around the credibility and reliability of the tipster and their information. More credibility is given to tipsters who identify themselves. Although there are many valid reasons why a tipster might want to remain anonymous, Illinois DUI Lawyers point out that a presumption exists that a witness willing to provide their name and address is passing on more reliable information than one who wishes to remain anonymous.

More credibility also adheres to tips providing strong levels of quantitative detail (like the make, model, color, location, and driving direction of a vehicle of a suspected DUI offender). For instance, in a Utah case where a caller (who did identify herself) reported that a defendant had been drinking (but not what or how much he had been drinking), the information was held to be insufficient to justify a stop by the police.

Illinois DUI Lawyers caution that a tip that provides detailed and verifiable information about a suspect's future behavior and movements is also generally considered credible and reliable, even if the informant remains anonymous. For example, in a Florida case, an anonymous tipster predicted a drug suspect's future movements (including when she would go to a particular hotel) with sufficient reliability to allow police to stop and arrest the suspect.

Chicago DUI Attorneys realize that stops based on anonymous tips that don't contain much detail have generally been held to be unlawful. A Texas court, for instance, stated specifically that police "generally cannot rely alone on a police broadcast of an anonymous phone call to establish reasonable suspicion."

This Illinois DUI Lawyer reminds you that courts are generally more lenient in allowing anonymous tips relating to drunken driving stops. For one thing, it's considered that a contemporaneous report of a suspected DUI violation would likely be credible and reliable than one relating to more personal crimes.

Courts generally find that intoxicated drivers present a far greater and more immediate threat to the public safety than some other risks. (For example, in a Florida case where a man was seen in passive possession of a gun, not threatening anyone, an anonymous tip was considered insufficient basis for a stop.) Stopping a driver on suspicion of DUI also does not violate the person's expectations of privacy and raise Constitutional concerns the same way that a stop and more intrusive search for a gun might do.

Your Chicago DUI Attorney points to a recent case out of the Illinois Appellate division that affirmed the right of officers to stop you for DUI on the basis of a tip. This case further articulated the officer's basis for stopping you. In People v. Hansen, 2-12 IL App (4th) 110603, April 3, 2012, the court applied the Shafer test to determine that the arresting officer had probable cause to stop the defendant on suspicion of DUI based upon a tip, even though the officer had not personally observed a traffic violation prior to receiving the tip.

Illinois DUI Lawyers are aware that People v. Shafer, 372 IL App. 3d 1044, 868 N.E. 2d 359 (2007) had resulted in a group of factors that should be used to determine the reliability of an informant's tip and whether a stop is justified. In Hansen, based on the Shafer test, the court found the tip sufficient to support a stop on suspicion of DUI by the police because:

  • The call made to a police emergency number to report the defendant making "donuts" in the middle of a road with his pickup truck was not an anonymous call.
  • The driver's reported conduct demonstrated a wanton and willful disregard for the safety of other persons and property.
  • The information provided by the caller was sufficiently quantitative and detailed to ensure that the officer stopped the right truck.
  • The time interval between the call to the police and the stop was brief.
  • The tip was based on contemporaneous eyewitness observations of the drunken driving.

The Court ultimately decided in Hansen that for reasons of public safety, a credible report of drunken driving should preclude a requirement that the arresting officer personally observe a traffic violation before making the stop. So if your stop and arrest resulted from a tip to police, that stop and arrest still might be valid. Your Illinois DUI Lawyer would need to carefully examine the particular facts of your case to discover your available defenses to the DUI charge.

Did the Stop by Police Violate Your Fourth Amendment Rights?

One of the leading cases that your Chicago DUI Attorney might use to answer this question came out of Illinois and went all the way to the U.S. Supreme Court. In Illinois v. Caballes, 543 U.S. 405 (2005), the U.S. Supreme Court addressed the issue of when a stop and search becomes unlawful because of its duration. In Caballes, an officer had pulled over a man who was speeding. Another nearby officer, a member of a drug interdiction squad, heard the report of the stop on the police radio and came to assist along with his trained drug-sniffing dog.

When the drug officer arrived, the first officer was still in the process of writing out a warning ticket. So the second officer walked around the car with his dog. The dog stopped and barked at the trunk as trained to do upon detecting drugs. Your Chicago DUI Attorney points out that this gave the officer probable cause to search the trunk, in which the officers found marijuana. So police arrested Caballes on a marijuana charge. His lawyer sought to have that charge thrown out, arguing that under the 4th Amendment it resulted from an illegal search and seizure.

This Illinois DUI Lawyer informs you that the U.S. Supreme Court affirmed the validity of the stop, search, and arrest, finding that use of the dog did not "unreasonably prolong" the initial routine traffic stop. (The first officer on the scene had still been writing the ticket when the dog made its find.) The entire incident lasted less than 10 minutes.


The Supreme Court's decision indicated that a routine traffic stop that itself justifies an officer to issue a warning does become an unreasonable search and seizure if it's prolonged beyond the time necessary to issue that warning. In this Illinois case, the search occurred while the warning ticket was still incomplete.


If, on the other hand, the first officer had completed and issued the ticket, but then prevented Caballes from leaving in order to wait for a drug team to come conduct a search, this Chicago DUI Attorney emphasizes that under the Caballes case, that hypothetical search might have been unlawful since the officer apparently did not have reasonable suspicion of a drug offense prior to the trained drug dog's barking.

The Supreme Court also found that no violation of the expectation of privacy occurred from the Caballes search since those in possession of illegal contraband have no lawful expectation of privacy in regards to that possession. Important note: Police conduct that does not violate a reasonable expectation of privacy is not considered a "search" under the 4th Amendment.

Did Your Charge Result from a DUI Roadblock?

Chicago DUI Attorneys understand that DUI Checkpoints and roadblocks are increasingly used throughout the nation as a means of trying to curb drunken driving. But if the primary purpose of the roadblock is to arrest drunken drivers (in other words, catch criminals and deter crime) rather than to enhance the public safety, the roadblock and your arrest might have been unlawful. And your Illinois DUI Lawyer might have a valid basis for getting your case dismissed.

Illinois DUI Lawyers realize that the primary means for determining the reason for the roadblock and checkpoint is often the officers' articulated statements. Good police officers might prepare for a court case and try to keep in mind that they must claim the primary purpose of public safety. But a careful line of questioning by a trial-hardened Chicago DUI Attorney could elicit a response indicating that the officer's primary purpose was to catch and arrest drunk drivers. This could make your stop and arrest invalid.


Chicago DUI Attorneys also rely on the court decisions that have formed a solid body of case law to guide judges, attorneys, and defendants in determining when roadblocks are developed and operated in a manner that violates your Constitutional rights. The U.S. Supreme Court, in Michigan v. Sitz, 496 U.S. 444 (1990), specifically held that a properly developed and operated DUI checkpoint program does not violate your 4th Amendment rights to be free from unreasonable search and seizure. Among the criteria to examine to determine whether a checkpoint/roadblock is properly planned and operated are:

  • Site selection for the checkpoint
  • Advance publicity concerning the checkpoint
  • Maintenance of safety conditions
  • The time and duration of the checkpoint
  • The length and duration of detention of stopped individuals
  • Procedural safeguards such as decision-making at the supervisory level, limits on officers' discretion, and indicators of the official nature of the roadblock

In a later case out of Indiana where a checkpoint involved a drug-sniffing dog walking around each vehicle, the U.S. Supreme Court held that the checkpoint violated Constitutional rights because its primary purpose was to detect evidence of ordinary crime. In other words, this Chicago DUI Attorney stresses that a general interest in crime control does not justify a checkpoint under the Constitution.


A stop at a checkpoint is essentially a stop without reasonable suspicion and must be legal and justified to be valid. In order to be lawful, the primary purpose of the checkpoint must be to enhance public safety (for instance, saving the public from the imminent dangers of drunken drivers out on the roads). One must look carefully at the words the police use to describe the purpose of the checkpoint.

The U.S. Supreme Court made a further distinction to show when checkpoints were valid stops in Illinois v. Lidster, 540 U.S. 419 (2004). That case involved a driver arrested for DUI at a checkpoint that had been set up at the time and site of a previous fatal hit and run accident in order to elicit helpful information from people who might have witnessed the accident. The officers were stopping each vehicle for a few moments to ask if anyone inside knew anything about the prior crime.

Your Chicago DUI Attorney notes that Lidster unfortunately happened to swerve upon approach to the checkpoint and run into one of the police cars. He was then arrested and later convicted for DUI. The Supreme Court upheld Lidster's arrest and conviction because the primary purpose of the roadblock had not been to arrest anyone, but only to elicit information relating to a prior crime.

Contact Experienced Chicago DUI Attorney Michael P. Schmiege if You Believe Police had No Reasonable Suspicion to Stop You or No Probable Cause to Arrest You for DUI

Each DUI case is unique with specific facts and circumstances that govern the lawfulness of the stop and arrest. The U.S. Constitution protects you from the danger of unreasonable searches and seizures by the police. But it takes a skilled and aggressive Illinois DUI Lawyer to accurately apply the law to the particular facts of your case and show that your Fourth Amendment Constitutional rights were violated. Your lawyer's strategically constructed legal arguments could then obtain suppression of the evidence against you.

There is sometimes a very fine line between what constitutes a legal, Constitutional stop and arrest on the part of the police and what does not. It takes diligent work on the part of your Illinois DUI Lawyer to set forth the facts, the clear legal arguments, and the law that justifies overturning your stop or arrest. If it were always clear what made a stop or arrest valid, such cases would never need to go as far as the U.S. Supreme Court for review. Don't let a possible rights violation lead to loss of your freedom. Seek the dedicated counsel and advocacy of Chicago DUI Attorney Michael Schmiege to ensure that you protect and preserve your rights under the law.

Experienced Chicago DUI Attorney Michael P. Schmiege offers you a free initial case evaluation and legal consultation. You and Mr. Schmiege could discuss the facts of your case and he could answer your questions about available defenses. Contact aggressive and dedicated Illinois DUI Lawyer Michael Schmiege today for your free consultation.

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