Forest Fires

Assuming the death penalty was acceptable, which means assuming that the justice system was infallible, I would execute forest fire arsonists. Regardless of age, regardless of mental condition. They are in a class of criminal that isn't merely a danger to particular individuals, but to society (and nature) as a whole. Society can't afford the risk of letting such persons ever go free, and death creates more certainty of that than even a "life" prison sentence.