The ideal is that all lives matter equally. But of course, they do not.
The lives of John Hinckley ad OJ Simpson mattered more than the lives of the several thousand men on death rows throughout the country. Money matters. Celebrity matters. If OJ had been only rich or only famous, he would have been on death row as well. Hinckley was not famous, and neither was his family, but being both rich and White made them matter more.
Scalia said that once a person had been sentenced to die, then the state was obliged to execute him, even though DNA was found to indicate his innocence.
Many studies of the death penalty have shown that Black men get the death penalty far more often than others in equivalent cases.
Ideally, the defense lawyers that poor people get stuck with are not nearly as qualified as the lawyers rich people hire, and that is another gross inequality issue that has not been addressed.