They are not 10 years old anymore so they can now be put to death? Is that convoluted thinking or what?

I noticed earlier that you said that they should be "sentenced" now; you never mentioned the possibility of a new trial. So you are saying that if one does something horrific at age 10 (or age 6? Or age whatever?) and survives to age 20 (or age 18?) that person should now be killed?

I wonder how you would go about it: On his or her 20th birthday, perhaps? Maybe at midnight there could be footsteps outside one's cell...