Illinois Rule of Evidence 705, which is substantially identical to its federal counterpart, reads as follows:

The expert may testify in terms of opinion or inference and give reasons therefor without first testifying to the underlying facts or data, unless the court requires otherwise. The expert may in any event be required to disclose the underlying facts or data on cross-examination.

In People v. Murray, 2019 IL 123289 (filed October 18, 2019), a jury convicted the defendant of first-degree murder and unlawful possession of a firearm by a street gang member (720 ILCS 5/24-1.8(a)(1)(a)). The defendant did not appeal the murder conviction, so the propriety of the firearm conviction was the only issue reviewed by the Illinois Supreme Court. 

A four-member majority of the court reversed the firearm conviction. It held that a detective’s testimony, as an expert witness on street gangs, failed to provide the jury all the elements listed in section 10 of the Illinois Streetgang Terrorism Omnibus Prevention Act ("the Act"; 740 ILCS 147/10), thus failing to define the Latin Kings
– the defendant’s alleged gang – as a street gang. The elements required by the Act include evidence that establishes the alleged street gang was involved in "a course or pattern of criminal activity" involving two or more gang-related felony offenses during specified time periods.  Based on the absence of such evidence, the majority held that the State had failed to establish the street gang status of the Latin Kings, and it thus failed to establish that the defendant was a street gang member.

The four justices in the majority agreed that, because the expert witness had not provided evidence that satisfied the Act’s statutory definitions of "street gang," the State failed to offer sufficient evidence to make its prima facie case. But two of the four justices in the majority provided an opinion in special concurrence refusing to join with the other two justices in their additional holding that Illinois Rule of Evidence 705 "unambiguously requires" experts to explain the reason underlying their opinions. The two specially concurring justices contended that the majority’s reliance on that aspect of its opinion created tension with the court’s long-standing statements in Wilson v. Clark, 84 Ill. 2d  186 (1981) and its progeny and, contending that that portion of the opinion was unnecessary, they rejected even the notion that Rule 705 applied, pointing out that "we need not consider how, or even if, Rule 705 and Wilson apply." Murray. at ¶ 60.

In a lengthy dissent, three members of the court contended that the expert witness’s testimony was sufficient to prove that the Latin Kings was a street gang and that the majority’s interpretation of the Act "will require the introduction of prejudicial evidence to convict a defendant based on crimes he personally may well have not committed or been involved in." Murray. at ¶ 71. Relevant to the interpretation of Rule 705, the dissent contended that the majority’s holding regarding the rule (an interpretation which, it must be stressed, had the concurrence of only two justices) contravenes controlling law, focusing on Wilson and other supreme court precedent, as well as Rule 705 itself and its interplay with IRE 703.

There are two takeaways from Murray, one based on a rule of evidence and the other relevant to prosecutions involving the offense of unlawful possession of a firearm by a street gang member:

•  Only two justices called for a different interpretation of Rule 705 than that provided by Wilson v. Clark and its progeny—an interpretation that has established the principles that an expert witness need not provide the underlying facts or data for an opinion and that the burden of attacking the opinion is placed on the party-opponent. The Wilson interpretation and that of its progeny has therefore not been altered.

•  Based on the holding of four of the seven justices, in future cases the State must accommodate the requirements of section 10 of the Illinois Streetgang Terrorism Omnibus Prevention Act for the presentation of prima facie evidence to prove a street gang’s identity.