In the state of Illinois, a person cannot be taken into police custody without some sort of evidence or reasonable suspicion that he or she was involved in a crime. In fact, people are legally allowed to walk away from a police officer unless they have been formally detained. If the officer prevents a person from leaving, that person has only been legally taken into custody if the officer had probable cause.
All United States citizens have the right to be free from unreasonable search and seizures under the Fourth Amendment of the U.S. Constitution. A search or seizure only becomes reasonable when law enforcement officers have probable cause. Probable cause must be established through evidence, observation or information derived from witnesses. Law enforcement officers can also establish probable cause through their expertise, such as if they detect tools that are often involved in certain crimes.
The arresting officer determines whether or not probable cause exists. However, a judge can later determine that the officer did not in fact have probable cause, meaning any evidence that was found when the person was taken into custody becomes inadmissible. On the other hand, the determination of probable cause is not affected if a person is charged but later found to be innocent.
Before a person can legally be taken into custody and face drug charges, the officers must have probable cause. However, there may be certain instances where an officer believes he or she has probable cause but the evidence is dubious. This can be subsequently be challenged by the defendant’s attorney.