In Miranda v. Arizona (1966), the Supreme Court of the United States required that custodial arrestees be informed of their constitutional and continuous rights to silence and to legal counsel. Moreover, the ruling mandated that waivers be considered valid only if they were made knowingly, intelligently, and voluntarily. However, in the decades that followed, evidence from both caselaw and empirical scholarship clarified that, for many vulnerable populations, these rights are in jeopardy. Among these vulnerable populations, those with limited cognitive capacities (LCCs) have been functionally excluded from research which primarily focused on persons with intellectual disabilities. This thesis offers a novel exploration of the role of specific cognitive impairments on Miranda comprehension and reasoning, with a focus on verbal intelligence (VIQ). Using a large archival sample of pretrial defendants (N = 820), current results suggest that defendants struggled with Miranda abilities regardless of other, individual characteristics. However, verbal intelligence emerged as a very strong predictor of Miranda comprehension such that those with lower VIQ were considerably more vulnerable to impaired comprehension. More so, data suggest that several compounded vulnerabilities (i.e., minoritized racial/ethnic identity status, limited academic achievement, illiteracy) are essential to understanding the extent of vulnerability in the criminal legal system in addition to the negative impacts of cognitive impairments. Several crucial implications for clinical practice and legal decision-making are explored. Finally, essential areas for future research are presented.

Nearly 700,000 suspects with mental disorders are arrested and Mirandized each year. The current study systematically examined the effects of cognitive deficits and psychological symptoms on both Miranda comprehension and reasoning. The current sample was comprised of 85 adult psychiatric inpatients recruited from University Behavioral Health (UBH), a private psychiatric hospital in North Texas. Unexpectedly, most inpatients demonstrated pervasive deficits in their immediate recall of a representative Miranda warning, omitting approximately four-fifths of its content. In addition, the majority of inpatients evidenced damaging errors in their reasoning about waiver decisions. As a result, 64.7% waived and subsequently confessed after only a 3-5 minute interrogation. Interestingly, impaired verbal ability but not the severity of their symptoms predicted greater deficits in Miranda comprehension.