Final answer:
Statements elicited from a defendant by placing an informant in their cell may be inadmissible because they could violate the Fifth Amendment's protection against self-incrimination, as per Miranda v. Arizona. The defendant must be informed of their Miranda rights; otherwise, statements may not be admissible in court.
Step-by-step explanation:
Any statements deliberately elicited from a defendant by an informant placed in their cell after appearing before a magistrate may be inadmissible in court, as they may violate the defendant's Fifth Amendment right to self-incrimination. This is based on the precedent set by the landmark case Miranda v. Arizona, wherein it was established that certain procedural safeguards must be in place to protect a person in custody from incriminating themselves without being aware of their rights.
Under Miranda rights, a defendant must be informed of their right to remain silent and their right to an attorney. If these rights are not communicated, and the defendant is not aware of these rights, the interrogations or any elicited statements may be considered a violation of the Fifth Amendment. However, in the given scenario, as the defendant had already been before a magistrate, it becomes a gray area whether the subsequent indirect interrogation through an informant would require a new Miranda warning.