for me im against for 3 reasons.
1) costs more. why should spend more money on someone to kill them?
2) innocence. the person might be innocent so its better to be able to free them.
3) 15-30 years of jail then death or 60-70 and randomly dying? you choose. i would go with death since at least i know that im gona get out of jail sooner (to the afterlife or whatever you believe in). i think living in jail is worse so that should be the punishment.