Knowing and intelligent: a study of Miranda warnings in mentally disordered defendants.

A conservative estimate is that 695,000 mentally disordered offenders are arrested and Mirandized annually in the United States. Past research has focused almost exclusively on cognitive factors affecting the comprehension of Miranda rights. The current study broadens the scope by including diagnostic variables and by extending the investigation to basic elements of Miranda reasoning. A sample of 107 mentally disordered defendants was administered two research measures, the Miranda Statements Scale (MSS) and Miranda Rights Scale (MRS), in addition to standardized tests. Most defendants lacked good comprehension of all but the simplest (Flesch-Kincaid<6th grade) Miranda warnings. Defendants with the poorest understanding (i.e., comprehending about 25% of the warnings) had marked deficits in multiple domains including cognitive abilities (intelligence and comprehension) and general adjustment. Different background and clinical variables predicted defendants' abilities to generate reasons either to exercise or waive their Miranda rights.