Watch any murder mystery, any reality court case, or any murder case on the news, the prime suspects are always the family, friends, and acquaintances of the deceased. While this may be true for murder mysteries (cases where no identifiable motive can be detected by the killing) generalizations from the “known aggressor theory” have been wrongly applied to murder as a whole. Now certain arguments in the crime prevention policy arena are standing on some shaky foundations.
Using stricter punishment policies to influence crime is a two sided debate. First, there’s the rational choice advocates who argue that increases in the degree and probabilities of punishment raises the costs to crime in the minds of calculating criminals. The other side of the argument claims that the majority of murders and violent crimes are performed by people who know the victim, they are crimes of passion or momentary intense emotions, the criminals themselves often quickly regret it. To the second group, raising the punitive level of law enforcement is not going to have a significant influence on these criminals, and it is often expensive.
While doing some reading today John Lott in More Guns Less Crime takes the second group to task on the empirics of their claim.

In interpreting the numbers, one must understand how these classifications are made. In this case, “murderers who know their victims” is a very broad category. A huge but not clearly determined portion of this category includes rival gang members who know each other. In larger urban areas, where most murders occur, the majority of murders are due to gang-related turf wars over drugs… While I do not wish to downplay domestic violence, most people do not envision gang members or drug buyers and pushers killing each other when they hear that 58 percent of murder victims were either relatives or acquaintances of their murderers.

While this insight does not tell us whether changes in the harshness or probability of punishment is more of a deterrent against crime, it certainly does insist that crime levels are influenced by sound policy and the institutional context created by legal policies rather than psychological or sociological factors.

If family members are included, 17 percent of all murders in Chicago for 1990-95 involved family members, friends, neighbors, or roommates remained virtually unchanged. What has grown is the number of murders by non-friend acquaintances, strangers, identified gangs, and persons unknown.