Is a defendant entitled to an objection at trial when the prosecution fails to disclose to the defense the facts supporting the objection?

Nor is a defendant without recourse when crucial evidence establishing the violation does not come to light until after the trial. A defendant is under no duty to object at trial if the defendant does not know, and could not reasonably discover, the facts supporting the objection. If, for example, the prosecution fails to disclose to the defense any material exculpatory evidence (see Brady v. Maryland (1963) 373 U.S. 83, 83 S.Ct. 1194, 10 L.Ed.2d 215), the defense may not learn of the undisclosed evidence until long after the trial has been completed. Therefore, when a claim depends substantially on facts that the defense was unaware of and could not reasonably have known at trial, a failure to object at trial will not bar consideration of the claim in a habeas corpus proceeding. We caution, however, that this exception applies only when the later discovered facts are essential to the claim. A habeas corpus petitioner may not avoid this procedural bar by relying on facts that, although newly learned, add

[17 Cal.Rptr.3d 639]

nothing of substance to what the defense knew or should have known at the time of trial. (See In re Robbins (1998) 18 Cal.4th 770, 814, fn. 34, 77 Cal.Rptr.2d 153, 959 P.2d 311.)⁵

[17 Cal.Rptr.3d 639]

We now apply these principles to each of the four claims at issue here.