In OJ's case his attorneys turned it into a race thing and used the black people on his jury like pawns. Other factors are counted in as well, like education level, etc.

I hope they someday execute David Westerfield, I don't know if anybody remembers his trial but he kidnapped, raped and killed a 7 year old girl. He is on death row in san quentin. Being white thankfully did not help him get out of his punishment.