Agood indicator that the death penalty applies to lower-class citizens is that of all the prisoners on death row have not finished high school.

The answer to this question is one-half
Not finishing high school is heavily correlated to poverty.
People who're having a hard time to fulfill their basic needs (food, clothes, and shelters) tend to have higher tendency to be involved in criminal activities which is more likely the reason of the situation above.

One-half of all people on death row do not have a diploma. This shows that, as school achievement level increases, there tends to be a negative correlation with death penalty application. The more achievement a person has during their school years, the less likely it is that they will be sentenced to death row.