Recent research (Erdodi et al., 2017) indicated that certain Wechsler Adult Intelligence Scale (WAIS-IV) Processing Speed Index (PSI)–based indices may have some utility as embedded validity indicators (EVIs) among a diagnostically diverse sample of neuropsychology referrals. Individuals with schizophrenia spectrum disorders (SSD) are often evaluated in forensic contexts in which there is incentive to exaggerate deficits. Because individuals with SSD often have limitations in processing speed associated with their disorders, the current study sought to evaluate the false-positive (FP) rates of cutoffs identified by Erdodi et al. on WAIS-IV PSI-based EVIs among forensically committed psychiatric inpatients with SSD who had no known incentive to feign because of the nature of their legal commitments. In the current sample, the previously suggested cutoff scores on PSI-based EVIs resulted in FP rates ranging from 2% to 57% among schizophrenia spectrum patients, with unacceptable FP rates for most indices. In the current sample of SSD patients, WAIS-IV PSI-based EVIs that are calculated based on the relative performance between PSI subtests (as opposed to absolute performance on individual indices) demonstrated acceptable FP rates.