What is the burden of a defendant in a criminal case to raise the issue of illegally obtained evidence?

It is the burden of the defendant in a criminal case to raise the issue of illegally obtained evidence (People v. Prewitt (1959) 52 Cal.2d 330, 335, 341 P.2d 1). When the defendant challenges the legality of a search and seizure, a showing that the search was made without a search warrant establishes a prima facie case and the burden of justification therefor then rests upon the People. (People v. Villalva (1973) 33 Cal.App.3d 362, 366, 109 Cal.Rptr. 16.) Prior to trial defendants noticed a motion to suppress evidence (Pen.Code, 1538.5). The motion was dropped before hearing at defendants' request. There were no other pretrial proceedings to suppress evidence nor did defendants during trial raise the claim now asserted. ²