La Griffe du Lion has a fascinating statistical analysis of race and criminality and describes a mathematical model that explains the black/white incarceration ratio and why most serial killers are white males.
Walsh identified 90 African American and 323 white American serial murderers, all men operating between 1945 and 2004. (Though Asians, Hispanics and Native Americans were not included in the study, their addition would not alter the fact that most serial killers are white men.) African American serial killers made up 22% of Walsh's sample, a figure in close agreement Hickey's enumeration. But, as blacks number well below 22% of the U.S. population, they are actually overrepresented among the ranks of serial killers -- roughly by a factor of 2.
So, why are most serial killers white men? The short answer is that serial murder is primarily a male enterprise, and in the U.S. white men outnumber black men seven to one. The long answer, however, is instructive.
The ratio of black to white criminal offenders generally increases with the progression from passive white collar crime to pernicious violent crime. In 2003, for example, blacks were imprisoned for violent crimes at approximately 7 times the per capita rate of whites, but only 4 times the white rate for property crimes. Serial murder, by any reckoning, ranks at the top of this progression. Consequently, black serial murderers should, per capita, outnumber their white counterparts by at least a factor of seven. In actuality, the factor is closer to two. The appropriate question, then, is not why most serial killers are white men, but rather why black men are only twice as likely as white men to be serial murderers. Criminality distributions provide the answer.
There's a bit of math, but Griffe's model of criminality is elegant in that it depends only on hard numbers rather than on unquantifiable concepts of justice or racism.