Justice Scalia warned in his dissent in ATKINS v. VIRGINIA, 536 U.S. 304, 122S.Ct. 2242 (2002) that the problem of feigned mental retardation would complicate the findings in cases involving the death penalty in low IQ individuals. Validity measurement in low IQ individuals has been criticized, largely with questions concerning specificity of performance validity tests (PVTs; Salekin & Doane, 2009, Applied Neuropsychology, 16, 105). In this article, our purpose is to examine the false positive rates of specific PVTs in low IQ individuals, particularly with reference to a Symptom Validity Scale previously developed for low functioning individuals (Chafetz, Abrahams, & Kohlmaier, 2007, Archives of Clinical Neuropsychology, 22, 1). The findings show that the PVTs analyzed have few false positives in a low IQ range of 60-75 when these individuals are well motivated to perform highly on testing, which allows these PVTs to be used in high stakes cases to provide evidence concerning malingering. Principles of dealing with performance validity in low functioning individuals are discussed with reference to the issues in capital cases. A practical summary guide is supplied.