65 ILCS 5/1-4-5
In case any injury to the person or property of another is caused by a member of the police department of a municipality having a population of 500,000 or over, while the member is engaged in the performance of his or her duties as a police officer, and without the contributory negligence of the injured person or the owner of the injured property, or the agent or servant of the injured person or owner, the municipality in whose behalf the member of the municipal police department is performing his or her duties as a police officer shall indemnify the police officer for any judgment recovered against him or her as the result of such injury, except where the injury results from the wilful misconduct of the police officer. A municipality, which is not otherwise required to indemnify pursuant to this Section, may indemnify a police officer for any judgment recovered against him or her for injuries sustained as a result of the police officer's performance of his duties as a police officer.
For the purposes of this section no civilian defense worker, nor any member of any agency engaged in any civilian defense activity, performing services as a part of any civilian defense program, shall be considered to be a member of a municipal police department.
If any person in obeying the command of any such police officer to assist in arresting or securing an offender is killed or injured or his or her property or that of his or her employer is damaged and such death, injury or damage arises out of and in the course of aiding such police officer in arresting or endeavoring to arrest a person or retaking or endeavoring to retake a person who has escaped from legal custody, the person or employer so injured or whose property is so damaged or the personal representatives of the person so killed shall have a cause of action to recover the amount of such damage or injury against the municipal corporation by which such police officer is employed at the time such command is obeyed.
65 ILCS 5/1-4-5