Wilson v. Clark
417 N.E.2d 1322, 84 Ill. 2d 186 (1981)
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Rule of Law:
An expert witness may base an opinion on facts or data not admitted into evidence, provided that information is of a type reasonably relied upon by experts in that particular field. The expert may also give their opinion without prior disclosure of the underlying facts, leaving it to the opposing party to elicit those facts on cross-examination.
Facts:
- Dr. David Clark provided medical treatment to John Wilson for his right leg.
- During the treatment, Wilson developed an infection in his leg.
- Dr. Clark's treatment focused on aggressive bacteria like staphylococci, while another organism, pseudomonas, was also present.
- Wilson's own expert witness, who performed the amputation, testified that the infection might have been cured if Wilson had been hospitalized on a specific earlier date.
- Ultimately, Wilson's right leg was amputated below the knee.
Procedural Posture:
- John Wilson sued Dr. David Clark for medical malpractice in the circuit court of Kane County, a trial court.
- Following a trial, the jury returned a verdict in favor of the defendant, Dr. Clark.
- Wilson, as appellant, appealed the judgment to the Illinois Appellate Court.
- The Appellate Court reversed the trial court's judgment and remanded the case for a new trial, finding error in the admission of evidence.
- The Supreme Court of Illinois then granted review of the case.
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Issue:
May an expert witness base an opinion on facts and data, such as hospital records, that have not been admitted into evidence, if that data is of a type reasonably relied upon by experts in the field?
Opinions:
Majority - Mr. Justice Moran
Yes. An expert witness may base an opinion on facts and data that have not been admitted into evidence, as long as it is the type of information reasonably relied upon by experts in that field. The court prospectively adopted Federal Rules of Evidence 703 and 705. Rule 703 allows an expert's opinion to be based on data that is not itself admissible, such as unauthenticated hospital records, because of the high degree of reliability of such documents. Rule 705 further modernizes procedure by allowing an expert to state their opinion without first disclosing all the underlying data, placing the burden on the cross-examining party to elicit the basis for the opinion. The court reasoned this change would eliminate the time-consuming process of posing long hypothetical questions and calling numerous authenticating witnesses. However, because this was a change in Illinois law, the court held it would be unfair to apply it retroactively to Wilson's case. Therefore, under the law in effect at the time of trial, the trial court committed reversible error by allowing an expert opinion based on improperly admitted hospital records.
Analysis:
This decision significantly modernized Illinois evidence law by aligning it with the Federal Rules of Evidence and the majority of other states regarding expert testimony. By adopting FRE 703 and 705, the court streamlined the process for admitting expert opinions, particularly in complex litigation like medical malpractice. The ruling shifts the procedural burden, requiring less time for foundational testimony on direct examination and placing more emphasis on cross-examination to vet the basis of an expert's opinion. This change promotes judicial efficiency and reflects a modern understanding of the reliability of data commonly used by professionals.
