Miranda understanding, appreciation, and reasoning abilities are essential to courts' determinations of knowing and intelligent Miranda rights waivers. Despite the remarkable development of Miranda research in recent decades, studies have generally focused on understanding and appreciation of Miranda rights, but have not examined Miranda reasoning and waiver decisions. Therefore, examining the nature of defendants' decisional capacities constitutes a critical step in further developing theoretical and clinical models for competent Miranda waiver decisions. The current study evaluated Miranda waiver decisions for 80 pretrial defendants from two Tulsa-area Oklahoma jails. Previously untested, the current study examined systematically how rational decision abilities affect defendants' personal waiver decisions. Components from general models of legal decision making, such as decisional competence and judgment models, were examined to determine their applicability to Miranda waiver decisions.