So Tsarnaev apologises for his crime. Predictable, as in the USA, showing remorse seems to infer some kind of leniency, on the American model “You’ll always be forgiven your fuckups and given a second chance”.
In business, you create a venture, it goes tits-up, you go bankrupt, you get a second chance. This is eminently fair, after all, your backers were venture capitalists who were fully aware that they might lose their shirt.
Tsarnaev’s case is very different, he maimed and killed. Purportedly in the name of a religion. Said religion does not, in its majority, condone maiming and killing, although it’s a fine line, given the lack of condemnation by the muslim community.
Let us be perfectly clear, the death penalty has little dissuasive effect (on psychotics, who by definition aren’t in ‘our’ world). The death penalty serves a simple purpose: the culprit cannot do it again and he cannot propagate his genes. There is no credible argument which would allow the remote possibility that Tsarnaev could reproduce; his crime is so ignominious that he must be eliminated.