107-12. Notice to appear. The arrest may be made with or without a warrant, depending on the circumstances.A police officer may make an arrest without a warrant if the officer witnesses a crime being committed. The police cannot arrest a person or search their property without a legal warrant. There are some exceptions however. A judge has to decide if a warrant should be issued or not. Sometimes the police need a warrant to conduct a search or make an arrest. (b) After an arrest without a warrant the person making the arrest shall inform the person arrested of the nature of the offense on which the arrest is based. (b) After an arrest without a warrant the person making the arrest shall inform the person arrested of the nature of the offense on which the arrest is based. Each state can enforce outofstate warrants through extradition proceedings, meaning you can be detained and transported back to Illinois.