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Investigatory stops and Driving Under the Influence (DUI) charges

It has not (yet) reached the point where the police can stop the operator of a motor vehicle for no reason whatsoever. You are protected from “unreasonable searches and seizures“. Judges decide where to draw the line between reasonable and unreasonable searches and seizures.

When you are in your house, the police are generally required to have more evidence before they can search your property and seize (arrest) you. In a motor vehicle, you enjoy a lower level of protection from unreasonable searches and seizures.

The police cannot stop a citizen just because “you look suspicious”. Courts have held that the police must have specific and articulable facts which, taken together with rational inferences from those facts, reasonably warrant the intrusion that a stop involves. These are known as invesitgatory stops.

If the police directly observe you committing a traffic violation, such as speeding, they are entitled to stop you for a brief enough period to investigate the traffic violation. That is where your troubles can start.

Once they do stop you for a routine traffic offense, they may then further their investigation if they believe you may be driving under the influence of alcohol. Common signs are an odor of alcohol, bloodshot eyes, slurred speech, open containers in the vehicle and difficulty locating your driver’s license, registration or insurance card.

The police are also entitled to investigate if they find you pulled over to the side of the road, or asleep in your vehicle or after you have been involved in an accident, even if the accident was not your fault. They are also, under proper circumstances, permitted to erect DUI roadblocks.

It can be more complicated when the police do not actually observe you committing an offense but have reason to believe that you may have. A citizen’s complaint, from someone whom the police have reasonable grounds to believe is reliable, will justify a stop.


But what happens if the police believe that you have done something wrong but you actually have not? If the officer reasonably believed that you may have done something wrong, even if that belief is factually inaccurate, the investigatory stop is valid. Therefore, he may be justified in taking it one step further in order to determine if there may be grounds to institute a DUI arrest.

The Illinois Vehicle Code (Rules of the Road) set forth rules for how loud your exhaust system can be. The police can stop you for a loud muffler. From there, he may be justified in investigating you for DUI.

Even if you are able to prove that your muffler was not louder than the legal limit, the initial stop is valid as long as the officer is able to show that he was reasonable in his belief that your muffler was too loud and that you had violated the law. The officer has merely committed a mistake of fact.

But suppose the police believe you have done something that constitutes a traffic offense, when in fact what you did was not illegal? This is known as a mistake of law. Such a stop is illegal and any further investigation, such as for DUI, is invalid.

In a recent case, the police officer observed the driver with his right turn signal engaged, yet despite having three opportunities to turn right, the driver did not. The officer claimed that the driver was guilty of improper use of a turn a signal.

The judges determined that not turning when a turn signal is engaged is not illegal. Therefore, because the police officer made a mistake of law, his decision to stop the driver was improper and the entire case had to be thrown out in order to protect the driver’s rights.

The son of Mike Ditka, former NFL tight end and Chicago Bears coach and now a football commentator for NBC, was recently arrested for DUI. Ditka claims he was arrested because of his name. Amidst all the hoopla, one other question that will have to be answered is, given that Ditka was apparently merely sitting in his vehicle, what legal justification did the police have for approaching him?

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