After you complete your research, you may have to include in your paper whether the death penalty should even be retained in the United States. There are those that believe it should be abolished and in fact, many western countries no longer have the death penalty. In the past few years, many death row inmates have been released due to new DNA evidence that exonerates them. Imagine how many may have been killed before any new DNA evidence could have freed them. And, as you have stated, a great many of the inamtes in prison today are minorities.
For an interesting viewpoint regarding this, I refer you to the work of Prison Fellowship and its founder, Chuck Colson, who was put in prison over his role in the Watergate scandal under President Nixon. After being released from prison, Colson started his ministry, Prison Fellowship, because he knows what it is like to be incarcerated and has a heart for prisoners - even the most vile offenders that throw feces at him when he visits the prisons. Colson's view is different from many others, and I encourage you to read about it.
Good luck on your research!