Accident Reconstruction Expert Witness Illinois: 3 Key Facts

Last Updated: October 25, 2026

Illinois Rule of Evidence 702 lets a qualified witness explain facts that call for specialized knowledge. The witness may testify in the form of an opinion when scientific, technical, or other specialized knowledge will assist the trier of fact to understand the evidence or to determine a fact in issue. The qualification may rest on knowledge, skill, experience, training, or education. Where the opinion uses a new or novel scientific methodology or principle, the proponent must show that it has gained general acceptance in that field. The rule was adopted September 27, 2010, effective January 1, 2011. Section 2-1116 still measures the injured person’s own share of the proximate cause.

What the Measurement Remains

735 ILCS 5/2-1116 diminishes damages when the plaintiff’s contributory fault is not more than 50 percent of the proximate cause, and it bars recovery when that share is more than 50 percent. The source is P.A. 103-1053, effective December 20, 2024. The section does not assign fault to one driver because that driver crossed a center line.

Photographs, vehicle damage, and roadway marks can be explained by a witness who has examined them when Rule 702 is met. Illinois Supreme Court Rule 213(f)(3) requires disclosure of a controlled expert’s subject matter, conclusions and opinions and their bases, qualifications, and any report about the case. Rule 208(e) provides that each party bears the fees charged by that party’s own controlled expert, unless manifest injustice would result. Rule 208(a) provides that the party at whose instance a deposition is taken pays the witness fee, the officer’s fee, and the recorder or stenographer for attending. The party who requests the transcript pays for the transcription. Rule 208 was amended December 29, 2017, effective January 1, 2018.

Frequently Asked Questions

Does a reconstruction opinion replace section 2-1116?

No. The section diminishes damages when the person’s own share is not more than 50 percent of the proximate cause, and it bars recovery above that share.

Does every case require an expert?

No. Rule 702 applies when specialized knowledge will assist the trier of fact. Section 2-1116 still measures the injured person’s own share of the proximate cause whether or not an expert testifies.

Does a low speed within the posted limit end the injury question?

A speed within the posted maximum does not decide whether an injury occurred. Rule 702 lets a qualified witness explain the damage, the roadway marks, and an opinion on the collision when that knowledge will assist the trier of fact. 625 ILCS 5/11-601(a) is a separate driving rule: a speed within the applicable maximum does not relieve the duty to decrease speed when a special hazard exists by reason of weather or highway conditions, or with respect to other traffic. The source is P.A. 104-787, effective August 7, 2026. The section does not name a feet-per-second figure.

When does section 13-202 require the action to be filed?

735 ILCS 5/13-202 requires the actions it covers to be commenced within 2 years next after the cause of action accrued. That two-year sentence does not cover damages resulting from first-degree murder or a Class X felony when the perpetrator is convicted of that crime. The source is P.A. 99-90, effective January 1, 2016. 735 ILCS 5/13-211(a) lets a person who was under 18 when a cause specified in sections 13-201 through 13-210 accrued bring the action within 2 years after attaining 18. That subsection does not state a general delayed-discovery exception.

Parker & Parker Attorneys at Law
300 NE Perry Ave., Peoria, IL 61603
Phone: 309-673-0069
Contact us

Schedule online for injury cases:
Injury scheduling

Need a lawyer? This article is part of our Peoria Car Accident Lawyer practice area. Call Parker & Parker at 309-673-0069 for a free consultation.

Accident Reconstruction and Expert Witnesses in Illinois Personal Injury Cases