[lukan]

A death sentence would certainly prevent this person from killing another child.

(Whether a death sentence is good for society in general is a different question)

[esafak]

It would not be good for a deceased either, especially if they are wrongly convicted.

[lukan]

Indeed, but it would also be not good to be wrongly sentenced to life in prison.

Once inside, chances to get out with a retrial are pretty slim.

Fatal misstakes are bad in any situation.