Impoverished defendants, as compared to those in the middle or upper-classes, are represented by incompetent, inexperienced legal counsel. Poor people comprise nearly all death row convictions, making the death penalty applicable, almost exclusively, to those of low socio-economic status.
Because a person doesn't fit into what the general population deems a person should be like doesn't mean that person deserves to die. (S)He is just as much a part of humanity and therefor we should create an image of society where everyone has their place. Even the most extreme people should fit in