Is there any case law where marijuana is seized by police officers?

The critical issue in the instant case would appear to be whether or not the officers had the right to be in the position to have plain view of the marijuana. (People v. Marshall, supra, 69 A.C. at p. 52, 69 Cal.Rptr. 585, 442 P.2d 665.) In other words, did the officers have probable cause to enter and arrest for a crime being committed in their presence and, as a corollary, did they have reason to believe the apartment was occupied? Finally, was section 844 of the Penal Code substantially complied with so that the officers did effect a proper entry?