Lawyers for both the plaintiff and defense should be aware of the implications for complex litigation of Illinois Rule 308, which allows for interlocutory appeals by permission. As a defense lawyer, I don't remember filing a Rule 308 motion, but lately, on the plaintiff's side, it seems I have had to defend a number of motions asking the trial court to allow the defendant to appeal an issue while the case in the trial court is still pending.
The fact that the defendant, in my experience, has never prevailed on the issue is probably because an interlocutory order is rarely suited to a Rule 308 appeal. According to Rule 308, in granting permission for an interlocutory appeal, the trial court must determine that the issue "involves a question of law as to which there is substantial ground for difference of opinion and that an immediate appeal from the order may materially advance the ultimate termination of the litigation."
The following is a section from a recently-filed memorandum that discusses the standard for granting a Rule 308 motion from the plaintiff's point of view. I appeared as co-counsel in the case and did not write the memorandum, although I did alter it slightly below. As in all cases in which I post the results of legal research, please don't use this language without doing your own independent study.
Illinois courts have consistently held that Rule 308 should be strictly construed and sparingly exercised. See Kincaid v. Smith, 252 Ill.App.3d 618, 622 (1st Dist. 1993); Voss v. Lincoln Mall Management Co., 166 Ill.App.3d 442, 445 (1st Dist. 1988); Camp v. Chicago Transit Authority, 82 Ill.App.3d 1107, 1111 (1st Dist. 1980); Getto v. City of Chicago, 92 Ill.App.3d 1045, 1048 (1st Dist. 1980). Rule 308 permits interlocutory appeals "only in exceptional cases where there are compelling reasons for rendering early determination of a critical question of law." Kincaid, 252 Ill.App.3d at 622. The rule was "not intended to open the floodgates to a vast number of appeals from interlocutory orders in ordinary litigation." Voss, 166 Ill.App.3d at 445, quoting Camp, 82 Ill.App.3d at 1110. For these reasons, the part seeking interlocutory appeal must overcome a significant burden.