Johannes Lopez was convicted of aggravated assaults, firearm offenses, criminal damage, and violations of Georgia’s Street Gang Act after two shooting incidents involving vehicles. At trial, the State presented experts about gang culture and Lopez’s alleged affiliation with SUR-13. The trial court excluded Lopez’s proposed gang expert because the witness lacked formal academic training and was not a specialized expert on SUR-13. The Court of Appeals held that exclusion was an abuse of discretion. Georgia law does not require formal education when a witness has specialized knowledge acquired through experience, and the proposed witness’s gang experience, investigation of gang cases, legal practice, and public work supplied a legally sufficient basis for qualification. The court reversed the Street Gang Act convictions because the excluded testimony could have addressed the State’s expert evidence. It affirmed the remaining convictions and rejected Lopez’s other claims, including challenges to a custodial statement and alleged ineffective assistance. The case therefore produced a partial reversal rather than a new trial on every count.