The short answer
Illinois Supreme Court Rule 224 allows a person to file a petition for discovery before suing, solely to identify who may be responsible for an injury.
Where it fits in your case
Before a lawsuit, when the potential defendant is unknown.
What to expect
Narrow purpose. It identifies potential defendants, not the merits of the claim.
Court order is required, and the respondent can object.
Common uses include identifying anonymous online posters.
What we need from you
Everything you know about the incident and any identifying details you have.
Common misconceptions
“It lets us investigate the whole case first.” It is limited to identity.
“It pauses the limitations clock.” Do not assume it does.