(720 ILCS 5/7-5) (from Ch. 38, par. 7-5)
    Sec. 7-5. Peace officer's use of force in making arrest. (a) A peace officer, or any person whom he has summoned or directed to assist him, need not retreat or desist from efforts to make a lawful arrest because of resistance or threatened resistance to the arrest. He is justified in the use of any force which he reasonably believes to be necessary to effect the arrest and of any force which he reasonably believes to be necessary to defend himself or another from bodily harm while making the arrest. However, he is justified in using force likely to cause death or great bodily harm only when he reasonably believes that such force is necessary to prevent death or great bodily harm to himself or such other person, or when he reasonably believes both that:
    (1) Such force is necessary to prevent the arrest from being defeated by resistance or escape; and
    (2) The person to be arrested has committed or attempted a forcible felony which involves the infliction or threatened infliction of great bodily harm or is attempting to escape by use of a deadly weapon, or otherwise indicates that he will endanger human life or inflict great bodily harm unless arrested without delay.
    (b) A peace officer making an arrest pursuant to an invalid warrant is justified in the use of any force which he would be justified in using if the warrant were valid, unless he knows that the warrant is invalid.
(Source: P.A. 84-1426.)