From John J. DiIulio Jr.'s analysis ("The Wacko-Vet Myth: Now echoed by the New York Times") of the Times's drive-by shooting ("Across America, Deadly Echoes of Foreign Battles"):

The Veterans of Foreign Wars (VFW) and other veterans' advocacy groups are absolutely correct that not merely "many" but the vast majority of veterans not only remain completely law-abiding but go on to lead stable and productive personal, professional, and civic lives. Assuming 121 homicide cases in relation to 749,932 total discharges through 2007, 99.98 percent of all discharged Iraq and Afghanistan veterans have not committed or been charged with homicide.

And assuming 121 cases and 749,932 total discharges, the homicide offending rate for the discharged veterans would be 16.1 per 100,000. The U.S. Bureau of Justice Statistics (BJS) has demographic data aplenty on homicide offending rates. For instance, in 2005, for white males aged 18-24, the rate was about 20 per 100,000. The Times opined that 121 was the "minimum" number, even as it counted veterans charged but not convicted with veterans tried and found guilty. Doubling the number to 242 would double the rate to 32.2 per 100,000.

Such crude but contextualizing calculations aside, the right question to ask is whether the veterans, other things being equal (controlling for age, race, gender, education, income, prior criminal history, and other variables), offend at rates that are significantly different from otherwise comparable groups (including groups that have an extreme PTSD incidence). Without doing the relevant statistical (multiple-regression) analyses with all the requisite empirical data, it is impossible to say.