What is the effect of a probation officer's "interview" on an appellant's right to waive his Miranda right?

Prior to his interview with the probation officer, appellant had refused to waive his rights and on several occasions sought to contact an attorney. Several hours later, appellant was again brought out for an "interview," this time by his probation officer, and was not even advised of his rights. The officer's first words to appellant were intended to and did convey that "this was a very serious case." In response, appellant made the admission in question. This was not a contact initiated by appellant, and his response to the officer's implied accusation could hardly have been unexpected. (See People v. White, supra, 69 Cal.2d at pp. 760-761, 72 Cal.Rptr. 873, 446 P.2d 993.) Obviously, it was not spontaneous. (See People v. Randall (1970) 1 Cal.3d 948, 958, 83 Cal.Rptr. 658, 664, 464 P.2d 114, 120 (once an accused has invoked his Miranda rights, a police-initiated interrogation "Cannot produce voluntary waivers or spontaneous statements.").)