Basically, when a member of one group attacks a member of another group, two things can happen that will affect homicide statistics: The aggressor can kill the victim, or the victim can kill the aggressor. The former act should be charged as a crime, the latter ruled justifiable (assuming the victim reasonably feared for life or limb). Therefore, more acts of aggression by members of a group translate to more unjustifiable homicides for that group and more justifiable homicides for the other group. As a result, if one group commits more violent crime, we’d expect that group’s homicides to be justified a lower percentage of the time.

You can follow the links above for more details on the math, but using a victimization survey by the Justice Department (which avoids the issue of racial bias in arrest statistics), a rough estimate is that there are 767,000 acts of black-on-white violence and 128,000 violent acts where the races were flipped in the U.S. annually. As I explained, if 2 percent of all victims of violence defend themselves, 128,000 acts of white-on-black violence inspire 2,500 acts of justified violence by blacks. And 767,000 acts of black-on-white violence inspire 15,000 acts of justifiable violence by whites. . . . As a result, 10 percent of white-on-black violence is justified, and only 0.3 percent of black-on-white violence is. This corresponds closely to the actual disparity from the FBI figures [regarding homicides ruled justifiable]: 11.41 percent to 1.2 percent.