In what circumstances will an expert opinion be considered in a civil case?

Here, the situation was very different. The relationship between Southside and Highland Street, defendant's membership in Southside, the Highland Street membership of some of the guests at the Costa residence on the night of the shooting, and the ongoing criminality of Southside were all matters beyond common knowledge. "[T]he decisive consideration in determining the admissibility of expert opinion evidence is whether the subject of inquiry is one of such common knowledge that men of ordinary education could reach a conclusion as intelligently as the witness or whether, on the other hand, the matter is sufficiently beyond common experience that the opinion of an expert would assist the trier of fact. [Citations.]" (People v. Cole (1956) 47 Cal.2d 99, 103, 301 P.2d 854.)