The three jurors who voted against the death penalty for Parkland killer Nikolas Cruz did so based on “mitigating circumstances” from Cruz’s life. They made the wrong call, but their rationale is superior to the reason many will agree with the sentence: a blanket opposition to the death penalty. Public support for capital punishment has slid over the last 30 years, remaining a majority opinion but barely so. Those who oppose death as a punishment often have kind, even noble intentions. Yet their well-meaning beliefs do not translate into justice or the common good. The death penalty is consistent with...