IL HB2221

Establishes framework for lay witness opinion testimony limited to observations that are rationally based on perception, helpful to understanding testimony, and not based on specialized knowledge.

Sets requirements for expert witness testimony including sufficient factual basis, reliable principles and methods, and reliable application to case facts; experts must be qualified in their particular field and cannot receive contingent compensation.

Requires mandatory pre-trial hearings upon motion to determine expert witness qualifications and whether testimony meets admissibility standards; courts must issue findings of fact and conclusions of law by final pre-trial hearing.

Mandates pre-trial disclosure of expert witnesses' identities and written reports containing opinions, bases, qualifications, publications within 10 years, compensation, and prior expert testimony within 4 years; disclosures due 90 days before trial or 30 days after opposing party's disclosure for rebuttal evidence.

Directs courts to follow U.S. Supreme Court standards in Daubert v. Merrell Dow Pharmaceuticals and related cases; permits interlocutory appeal of expert evidence rulings at appellate court discretion and establishes de novo review for legal questions and abuse of discretion standard for factual applications.