In 2005, the U.S. Supreme Court struck down the death penalty for those younger than 18 when they killed, repeatedly quoting an article by psychologists Laurence Steinberg and Elizabeth Scott. But in the same article, these leading developmental psychologists themselves characterized it as an “open question whether under real-world conditions the decision making of mid-adolescents is truly comparable with that of adults.” And they were talking about 17-year-olds.

To the best of my knowledge, science has not and cannot establish a definitive connection between organic brain development and moral responsibility.

Think about it: When a 19-year-old bravely dashes into a burning building, risking his life to save children inside, we celebrate this heroism. We do not, nor should we, dismiss this bravery as the product of an impulsive not-yet-fully-formed personality. If we can fully celebrate good character and heroic acts of our best young adults, why can’t we fully condemn the cowardly viciousness of our worst?