What is the current state of the law on whether a confession is voluntary?

^18. In People v. Boyette, the issue before the trial court was whether the defendant's confession was voluntary. (29 Cal.4th at p. 412.) In J.D.B. v. North Carolina, the issue was whether the accused juvenile would consider himself to have been in custody. (131 S.Ct. at p. 2406.)

^19. "'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., subd. (a).) The subject matter of the culture and habits of criminal street gangs . . . meets this criterion.'" (People v. Vang (2011) 52 Cal.4th 1038, 1044 (Vang).)