The trial court did not err by allowing a police officer’s expert testimony concerning gangs and gang activity. Appellants were convicted of conspiring to commit the crimes of shooting from a vehicle and assault with a semiautomatic firearm with gang enhancements. At their trial, Officer Krish, testifying as a gang expert, opined appellants were members of the Lowell Street gang and intended to commit a violent act for the gang’s benefit. His opinions were based on conversations with gang members and other officers, as well as written materials. On appeal, appellants argued Krish’s testimony about the background and history of the El Sereno and Lowell Street gangs should have been excluded because it was based on hearsay and violated their confrontation rights. The Court of Appeal affirmed, holding the trial court did not err by admitting this testimony. Krish did not rely on hearsay sources alone or just recite others’ statements. He fit this information in with all his other sources of information and also relied on his six years of experience as a police officer, which included nearly two years in the gang enforcement division, and his substantial training. His testimony did not violate the confrontation clause because the out-of-court statements he relied on were not testimonial.