In In re Alexander L. (2007) 149 Cal.App.4th 605, the gang enhancement was based upon testimony of a gang expert who, when asked about the gang's primary activities, responded " 'I know they've committed quite a few assaults with a deadly weapon, several assaults. I know they've been involved in murders. I know they've been involved with auto thefts, auto/vehicle burglaries, felony graffiti, narcotic violations.' " (Id. at p. 611.) The expert did not explain the basis for his knowledge or provide the details of any particular crimes, nor did he "directly testify that criminal activities constituted the gang's primary activities." (Id. at p. 612.) The appellate court noted, "even if we could reasonably infer that the gang expert meant that the primary activities of the gang were the crimes to which he referred, his testimony lacked an adequate foundation." (Ibid.) Consequently, the appellate court concluded that there was insufficient evidence that the "primary activities" prong essential to proving the existence of a criminal street gang had been established. (Id. at pp. 611-612.)