I support the death penalty in the cases where there is no doubt whatsoever, but not with the laborious appeals process. Justice should be swift IMO. I also think the next of kin of the victim should have a right to make it a life sentence if they want. After all, if the victim's family doesn't want the guy dead, then why should the rest of us!?
As for adulthood vs. childhood, I am for a world in which boys count as adults at 16, girls at 14. Of course with today's banal upbringing practices that's rather impractical, but when adults take more responsibility for their children and pass less of it to society, it can be a reality.
But to say they're adults for justice purposes, but children for alcohol and gambling purposes, that's just ludicrous and hypocritical.