Because, statistically speaking, race is a good predictor of violent crime. According to Bureau of Justice statistics, between 1976 and 2005, blacks, while 13

Because, statistically speaking, race is a good predictor of violent crime. According to Bureau of Justice statistics, between 1976 and 2005, blacks, while 13 percent of the population, committed over 52 percent of the nation’s homicides, or about 400% more than expected. However, poor people (arbitrarily defining poor as a household income of under $25k) only account for ~double as many crimes as expected. (The government doesn't actually keep data on income of violent crime perpetrators - I used the household income of violent crime victims from http://www.ojp.usdoj.gov/bjs/abstract/cv05.htm http://www.ojp.usdoj.gov/bjs/abstract/cv05.htm weighted by census data from http://pubdb3.census.gov/macro/032007/hhinc/new06_000.htm http://pubdb3.census.gov/macro/032007/hhinc/new06_000.htm as a proxy) Now, maybe income is a better predictor; I couldn't say conclusively with the data at hand. But you have to agree that race is pretty important.