<p>This simulation study sought to investigate a response style marked by simultaneous over- and under-reporting (OR + UR) in a criminal forensic evaluation context. Using a known groups design, Whitman et al. (2023) previously examined the impact of simultaneous OR + UR in a sample of civil disability claimants, finding it to be associated with higher scores on symptom validity tests, a higher likelihood of producing scores indicative of noncredible responding on performance validity tests, higher scores on measures of psychopathology (except those related to externalizing dimensions, which were lower), and lower scores on performance-based cognitive tests when compared with claimants who engaged in over-reporting only (OR-only). The current study utilized a simulation design to investigate OR + UR relative to an OR-only response style and genuine responding using the MMPI-3 in a simulated criminal forensic context. College student participants completed a battery of measures covering a broad range of psychopathology following standard instructions (SI). They then completed the MMPI-3 under one of three instructional manipulations: SI, OR-only, or OR + UR. The OR + UR group produced higher OR scale scores than the SI group and higher L scores than the SI and OR-only groups. Classification accuracy estimates supported use of the MMPI-3 Validity Scales for identifying OR-only and OR + UR response styles, particularly with respect to specificity. Finally, both the OR + UR and the OR-only response manipulations led to attenuation of validity coefficients for the MMPI-3 substantive scales.</p>