Sub-average Intellectual Functioning Law and Legal Definition

Sub-average intellectual functioning is defined as “an IQ of about 70 or below (approximately 2 standard deviations below the mean). IQ tests may overstate or understate the subject's actual level of intellectual functioning. Psychologists and other mental health professionals are flexible in their assessment of mental retardation; thus, sometimes a person whose IQ has tested above 70 may be diagnosed as mentally retarded while a person whose IQ tests below 70 may not be mentally retarded.” Moore v. Quarterman, 2009 U.S. App. LEXIS 19015 (5th Cir. Tex. Aug. 21, 2009)