Putting Tsarnaev to death won't serve any purpose at all. Some may feel better for a short moment, but their loved ones are gone forever and their wounds will never be completely healed. It won't deter anybody and Tsarnaev will only get off easier than rotting in prison for the rest of his life. And the whole notion of "retributive justice" is useless to society.
As of those who feel happy about a fellow man being executed without having any connection to the case, I can't help thinking of them as a bit bloodthirsty. "Justice is served" is a pathetic excuse for their own primitive instincts.
This isn't manslaughter or second degree murder, it's first degree premeditated murder. There's no doubt about who committed the murder. It wasn't just 1 killing, it was 4, 1 of which was done to a minor and another of which was done to a police officer for the purpose of escaping punishment. It wasn't done because one of the victims did something to provoke him, it was murder for the sake of murder. The people on the jury came in with varying views on the death penalty.
There is literally no legitimate reason not to kill him. I'm sorry, but blaming one's brother or the state's perceived ideolological bias is not an acceptable reason to keep a criminal alive. He has lost all right to life, and no other punishment besides death fits his crime.
To those who say 'we're ridding the world of evil!!' I have to ask why? My personal ethical and moral opposition to the death penalty aside, I have to ask why. Why the death penalty when he'll never ever get out of that prison in Colorado to hurt someone ever gain. What does this seek to achieve other than creating a martyr to be held in high regard. You're giving him the short end of the stick.
I won't get into a huge debate because this is one of the few political issues where I form my opinion largely with my "gut" more than with cold, hard logic, but I will at least give you the courtesy of a response: there are certain people who have so disrespected others' lives that I think they need to lose the very thing they took. I know, I know, the prison might be worse than death, he'll likely never escape and it really doesn't do anyone "any good" to execute him ... but I do not think he deserves to even inhale another breath or have another thought; I don't think he deserves one more second of being conscious or sentient.
I'm sure that sounds ridiculous to many, but that's how I feel.