Article III. Civil Appeals Rules · Part D. Briefs · Last amended 2010 · Last verified July 20, 2026
In one sentenceRule 345 lets outside parties file friend-of-the-court briefs, but only with the court's permission and under the same format rules as the party they support.
(a)Leave or Request of Court Necessary. A brief amicus curiae may be filed only by leave
of the court or of a judge thereof, or at the request of the court. A motion for leave must be accompanied by the proposed brief and shall state the interest of the applicant and explain how an amicus brief will assist the court.
(b)Forms; Conditions; Time. A brief of an amicus curiae shall follow the form prescribed for the brief of an appellee, shall identify the amicus as such on the cover of the brief, and shall conform to any conditions imposed by the court. Unless the court or a judge thereof specifies otherwise, it shall be filed on or before the due date of the initial brief of the party whose position it supports. The color of the cover shall be the same as that of the party’s brief whose position it supports.
(c)Oral Argument. Amicus curiae will not be allowed to argue orally.
Plain-English Summary
An amicus curiae brief comes from someone who isn't a party to the appeal but has a stake in how the court rules. Rule 345 makes clear that filing one isn't automatic — a would-be amicus needs leave of the court, or the court has to invite the filing.
The motion asking for leave must come with the proposed brief attached, and it has to explain the applicant's interest in the case and how the brief will help the court decide it. Once permitted, the amicus brief follows the same format required of an appellee's brief, labels itself as an amicus filing on the cover, and matches the cover color of the party it supports. It's typically due the same day as that party's brief.
One thing an amicus never gets under this rule is a seat at oral argument — that privilege stays with the actual parties to the case.
Frequently Asked Questions
Can anyone file an amicus curiae brief in an Illinois appeal?
No. Filing one requires leave of the court or a judge, or an invitation from the court itself.
What has to be in the motion asking for leave to file?
The proposed brief itself, plus a statement of the applicant's interest in the case and an explanation of how the brief will assist the court.
What format does an amicus brief follow?
The same format prescribed for an appellee's brief, with the cover identifying it as an amicus filing and colored to match the brief of the party it supports.
When is an amicus brief due?
On or before the due date of the initial brief filed by the party whose position it supports, unless the court sets a different date.
Can amicus counsel take part in oral argument?
No. Rule 345 flatly bars amicus curiae from arguing orally.
Amendment History
Amended February 19, 1982, effective April 1, 1982; amended May 28, 1982, effective July 1, 1982; amended December 17, 1993, effective February 1, 1994, amended December 6, 2005, effective immediately; amended September 20, 2010, effective immediately.
Source & verification. Rule text, official Committee Comments, and
amendment history are reproduced verbatim from the Illinois Supreme Court Rules,
promulgated by the Supreme Court of Illinois. Last verified July 20, 2026.
· Official source
Also known as:amicus curiae brieffriend of the court briefamicus brief formatleave to file amicus briefthird-party brief in appeal