720 ILCS 5/14-1
An eavesdropping device is any device capable of being used to hear or record oral conversation or intercept, or transcribe electronic communications whether such conversation or electronic communication is conducted in person, by telephone, or by any other means; Provided, however, that this definition shall not include devices used for the restoration of the deaf or hard-of-hearing to normal or partial hearing.
An eavesdropper is any person, including any law enforcement officer and any party to a private conversation, who operates or participates in the operation of any eavesdropping device contrary to the provisions of this Article or who acts as a principal, as defined in this Article.
A principal is any person who:
For the purposes of this Article, "private conversation" means any oral communication between 2 or more persons, whether in person or transmitted between the parties by wire or other means, when one or more of the parties intended the communication to be of a private nature under circumstances reasonably justifying that expectation. A reasonable expectation shall include any expectation recognized by law, including, but not limited to, an expectation derived from a privilege, immunity, or right established by common law, Supreme Court rule, or the Illinois or United States Constitution.
For purposes of this Article, "private electronic communication" means any transfer of signs, signals, writing, images, sounds, data, or intelligence of any nature transmitted in whole or part by a wire, radio, pager, computer, electromagnetic, photo electronic or photo optical system, when the sending or receiving party intends the electronic communication to be private under circumstances reasonably justifying that expectation. A reasonable expectation shall include any expectation recognized by law, including, but not limited to, an expectation derived from a privilege, immunity, or right established by common law, Supreme Court rule, or the Illinois or United States Constitution. Electronic communication does not include any communication from a tracking device.
For purposes of this Article, "bait car" means any motor vehicle that is not occupied by a law enforcement officer and is used by a law enforcement agency to deter, detect, identify, and assist in the apprehension of an auto theft suspect in the act of stealing a motor vehicle.
For purposes of this Article, "surreptitious" means obtained or made by stealth or deception, or executed through secrecy or concealment.
720 ILCS 5/14-1