When will a court order a search and seizure of a quantity and quality of illegal drugs seized at a police station?

We acknowledge that the quantity and quality of the contraband seized is always relevant to the issue of whether narcotics are held for sale or personal use (People v. Shipstead (1971) 19 Cal.App.3d 58, 77, 96 Cal.Rptr. 513), and that persons charged with drug offenses have a significant interest in having an opportunity to examine, and perhaps have chemical tests performed on, evidence to be offered against them. (See People v. Backus (1979) 23 Cal.3d 360, 384, 152 Cal.Rptr. 710, 590 P.2d 837.) The state may not arbitrarily deny such a right or foreclose a defendant from securing potentially favorable evidence. (See People v. Nation (1980) 26 Cal.3d 169, 176, 161 Cal.Rptr. 299, 604 P.2d 1051.)