What is the test for expert testimony in a criminal case?

"California law permits a person with 'special knowledge, skill, experience, training, or education' in a particular field to qualify as an expert witness (Evid. Code, 720) and to give testimony in the form of an opinion (id., 801). Under Evidence Code section 801, expert opinion testimony is admissible only if the subject matter of the testimony is 'sufficiently beyond common experience that the opinion of an expert would assist the trier of fact.' (Id., at subd. (a).) The subject matter of the culture and habits of criminal street gangs . . . meets this criterion." (People v. Gardeley (1996) 14 Cal.4th 605, 617.)