In what circumstances will a defendant in a murder case give a statement that he stabbed a fellow inmate in the yard?

In People v. Roldan (2005) 35 Cal.4th 646, the defendant was standing in the jail food line when he saw a deputy he knew. The defendant asked the deputy, "'"What's happening ....?"'" The deputy recognized the defendant and asked if he was going to stay out of trouble. The defendant responded, "'"Yeah, it was nothing. I don't know why they are bothering with all this court. I am guilty. I [stabbed] that guy in the yard."'" Later when the deputy transported the defendant back to a high security area, the defendant asked why he was being moved. The deputy said it was for his own protection. The defendant replied, "'"It is no big deal. I don't know why. I am probably going to face the death penalty anyway."'" Our Supreme Court held that defendant's statements were volunteered and not made in response to interrogation. (Id. at pp. 735-736, overruled on another ground in People v. Doolin, supra, 45 Cal.4th at p. 421, fn. 22.)