What is the test for establishing that a criminal street gang is a "criminal street gang"?

To prove that a gang is a "criminal street gang," the prosecution must show that the gang has as one of its "primary activities" the commission of one or more of the crimes enumerated in section 186.22, subdivision (e). ( 186.22, subds. (e), (f).) "The phrase 'primary activities,' as used in the gang statute, implies that the commission of one or more of the statutorily enumerated crimes is one of the group's 'chief' or 'principal' occupations," as opposed to the occasional commission of those crimes by one or more of the group's members. (People v. Sengpadychith (2001) 26 Cal.4th 316, 323.) "Sufficient proof of the gang's primary activities might consist of evidence that the group's members consistently and repeatedly have committed criminal activity listed in the gang statute." (Id. at p. 324.) "The testimony of a gang expert, founded on his or her conversations with gang members, personal investigation of crimes committed by gang members, and information obtained from colleagues in his or her own and other law enforcement agencies, may be sufficient to prove a gang's primary activities. [Citations.]" (People v. Duran (2002) 97 Cal.App.4th 1448, 1465.)