How has the court applied the exclusionary rule of People v. Cahan to cases pending on appeal?

The historic pattern of applying the court's current expression of a basic principle to cases pending on appeal finds numerous classic illustrations. Thus, for example, we applied the exclusionary rule of People v. Cahan (1955) 44 Cal.2d 434, 282 P.2d 905, 50 A.L.R.2d 513, to a case 'tried before the decision in People v. Cahan * * * at a time when the trial court was bound by the earlier decisions of this court that illegally obtained evidence was admissible' (People v. Kitchens (1956) 46 Cal.2d 260, 262, 294 P.2d 17, 19); yet we have held that a defendant may not collaterally[425 P.2d 548]

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