A particular problem with executions in the U.S., but probably in many other capital punishment countries as well, is racial discrimination. Whereas U.S. citizens from African-American descent make up only 12 or 13% of the population, they represent 34% of the executions:
The racial discrepancy is even larger when you look at the people on death row:
The race of the murder victim also plays a role: a murder of a white person is more likely to result in capital punishment for the perpetrator.
see more (re-blogged from): http://filipspagnoli.wordpress.com/stats-on-human-rights/statistics-on-capital-punishment/#7