People v. Valencia, 489 P.3d 700

Early morning shooting at an Arvin carwash; Valencia (driver) and Garcia (passenger) were chased and arrested; gunshot residue and a revolver cylinder were recovered near the pursuit.
Both defendants were charged with attempted murder, assault with a firearm, active gang participation (Pen. Code, §186.22, subd. (a)) and gang enhancements (Pen. Code, §186.22, subd. (b)), among other counts.
Arvin police Officer Ryan Calderon testified as a gang expert about Arvina 13 (territory, symbols, activities) and recited the facts of three predicate offenses based on police reports and conversations with other officers; Calderon had no personal knowledge of those predicate facts.
Certified court documents showing convictions in the predicate matters were admitted, but no witness with personal knowledge testified to the factual particulars of those predicate offenses.
The Court of Appeal held the expert’s case-specific recitations were inadmissible hearsay and reversed the active participation findings, related enhancements, and some firearm enhancements; the Supreme Court granted review and consolidated the appeals.
The Supreme Court affirmed: under Sanchez and Veamatahau, predicate-offense facts are case-specific and cannot be proved solely by an expert’s out-of-court statements; the error here was not harmless beyond a reasonable doubt.

Issue	Plaintiff's Argument	Defendant's Argument	Held
Whether facts of predicate offenses may be proved by a gang expert’s recounting of police reports and other out-of-court statements as "background"	Expert testimony sufficed; predicate details are background information the expert may relate	Sanchez bars experts from supplying case-specific hearsay; predicate facts require independent admissible proof	Predicate-offense particulars are case-specific; must be proved by independently admissible evidence; expert may not supply them via hearsay
Standard and effect of the hearsay error	Any error was harmless beyond a reasonable doubt because the expert otherwise proved gang membership and conduct	Admission of testimonial hearsay requires Chapman review and was prejudicial here	The error implicated confrontation/testimonial concerns; under Chapman it was not harmless beyond a reasonable doubt and required reversal of the gang findings/enhancements

People v. Sanchez, 63 Cal.4th 665 (establishing limits on expert testimony that relays case-specific hearsay)
People v. Veamatahau, 9 Cal.5th 16 (distinguishing background expert reliance from impermissible case-specific hearsay)
Crawford v. Washington, 541 U.S. 36 (confrontation clause bars testimonial hearsay unless old testimony/unavailability and cross-examination)
Chapman v. California, 386 U.S. 18 (harmless-error standard for federal constitutional errors)