Yes, as held in State v. Sims, if the Court determines that the waiver was not signed knowingly, intelligently and voluntarily then that waiver is considered ineffective and the defendant’s Fifth Amendment Rights can still be violated.
The right against self-incrimination is guaranteed by the Fifth Amendment to the United States Constitution, and by New Jersey statutes. The historic 1966 U.S. Supreme Court case Miranda v. Arizona, requires law enforcement to inform individuals in police custody of these rights prior to questioning.
Generally, by signing a waiver of these rights, an individual who is in police custody acknowledges that they are not being pressured or coerced to provide information to law enforcement personnel. However, there are exceptions to this general proposition.