What is the defense argument that the prosecution suppressed material evidence that might have been favorable to the defense?

The defense raises two other theories, first, that the prosecution suppressed substantial material evidence favorable to the defense (People v. Ruthford (1975) 14 Cal.3d 399, 121 Cal.Rptr. 261, 534 P.2d 1341); and second, that the prosecution failed to preserve evidence which might have been favorable to the defense (People v. Hitch (1974) 12 Cal.3d 641, 117 Cal.Rptr. 9, 527 P.2d 361). These theories are not based on a specific court order but due process.