The inverse correlation between mean white IQ (as estimated by NAEP scores) and the white homicide offender rate at the state level in the US is a statistically significant .67 (p = 0).
A few technical notes: Florida is excluded for lack of adequate FBI uniform crime reporting data. "White" includes Hispanics who racially identify as white. To compute the total white NAEP scores for each state, I took NAEP results for 8th graders from 2005 and then weighted the non-Hispanic white and Hispanic scores according to how much of the total white test-taking population each comprised. For the states in which the Hispanic population is too small to be reliably reported, I used the average Hispanic score from the states where the Hispanic populations are large enough for mean scores to be reported.
Intelligence doesn't just improve quality of life measures in a cerebral way, it also does the physical body good.