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.