740 ILCS 40/5
The plaintiff at any time before, but not later than 10 days after, the filing of the answer, unless further time be granted by the court, may file interrogatories in writing concerning matters material to the allegations of the complaint or respecting the ownership of the property upon which it is claimed the nuisance is maintained. A full answer to each interrogatory under the oath of the defendant shall be filed with the clerk within 10 days after a copy of the interrogatories has been served upon him. For a failure to so answer interrogatories the court may strike the answer to the complaint from the files and enter an order of default and final judgment, and a rule to answer interrogatories may be entered and the court may punish a defendant for contempt of court for a refusal to obey such rule. No person shall be excused from answering interrogatories under oath on the ground that an answer may tend to incriminate him or subject him to a penalty or forfeiture. The answer shall be evidence against, but not on behalf of, the defendant and it and evidence derived from it shall not be used against him in any criminal proceeding other than as rebuttal evidence to testimony given by the defendant or in a case for perjury.
740 ILCS 40/5