Ill. R. Evid. 702
If scientific, technical, or other specialized knowledge will assist the trier of fact to understand the evidence or to determine a fact in issue, a witness qualified as an expert by knowledge, skill, experience, training, or education, may testify thereto in the form of an opinion or otherwise. Where an expert witness testifies to an opinion based on a new or novel scientific methodology or principle, the proponent of the opinion has the burden of showing the methodology or scientific principle on which the opinion is based is sufficiently established to have gained general acceptance in the particular field in which it belongs.
Ill. R. Evid. 702
Comment
Rule 702 confirms that Illinois is a Frye state. The second sentence of the rule enunciates the core principles of the Frye test for admissibility of scientific evidence as set forth in Donaldson v. Central Illinois Public Service Co., 199 Ill.2d 63, 767 N.E.2d 314 (2002).