What if the guy killed two people from different famileis, one who thinks the death penalty is evil the other who wants the death penalty? What of people who have no families?
Oh and in general I think it's a bad idea to leave decisions like that to people who have a strong emotional attachment to them.
Tell you what dumbo, try for a moment to put yourself in the shoes of those you think shouldn't have a say and see what answer you come up with, if it is the wring answer go fuck yourself then try again.
Society will be effected by their decision whatever it is.
If they deicde a long prison term, society has to foot the bill.
If they decide a short term then we will release a dangerous man back into society possibly without appropriate punishment.
If death the state has to kill them.
As it stands now the only thing family members can do is drop charges for certain crimes.