In People v. McKown, 226 Ill. 2d 245, 254, 875 N.E.2d 1029, 314 Ill. Dec. 742 (2007), our supreme court held that "a court may determine the general acceptance of a scientific principle or methodology in either of two ways: (1) based on the results of a Frye hearing; or; (2) by taking judicial notice of unequivocal and undisputed prior judicial decisions or technical writings on the subject." The trial court's determination of admissibility under Frye v. United States, 293 F. 1013 (D.C. Cir. 1923) is subject to de novo review. In re Commitment of Simons, 213 Ill. 2d 523, 529-30, 821 N.E.2d 1184, 290 Ill. Dec. 610 (2004). Moreover, "in conducting such de novo review, the reviewing court may consider not only the trial court record but also, where appropriate, sources outside the record, including legal and scientific articles, as well as court opinions from other jurisdictions." Simons, 213 Ill. 2d at 531; see also McKown, 226 Ill. 2d at 259.