710 ILCS 35/5

(a) A privilege under Section 4 may be waived in a record or orally during a proceeding if it is expressly waived by all parties to the mediation and: (1) in the case of the privilege of a mediator, it is expressly waived by the mediator; and (2) in the case of the privilege of a nonparty participant, it is expressly waived by the nonparty participant. (b) A person that discloses or makes a representation about a mediation communication which prejudices another person in a proceeding is precluded from asserting a privilege under Section 4, but only to the extent necessary for the person prejudiced to respond to the representation or disclosure. (c) A person that intentionally uses a mediation to plan, attempt to commit or commit a crime, or to conceal an ongoing crime or ongoing criminal activity is precluded from asserting a privilege under Section 4.