Ill. R. Evid. 602
As amended through September 23, 2024
A witness may not testify to a matter unless evidence is introduced sufficient to support a finding that the witness has personal knowledge of the matter. Evidence to prove personal knowledge may, but need not, consist of the witness' own testimony. This rule is subject to the provisions of Rule 703, relating to opinion testimony by expert witnesses.
Ill. R. Evid. 602