With my devil's advocate hat on, I present the following: Something to consider when these instances are with adults under 30, they may just be developmentally delayed in a specific way. Your prefrontal cortex continues to mature into the mid 20s on average, the last portion of the brain to mature and this has serious implications for decision making skills. And for any who engaged with drugs heavily and early (to include alcohol), this could actively slow if not stop further development in this crucial region.
But this is why we generally still make some really stupid decisions early in our adult lives, and some of them leave people seeming like they never matured past high school.
Not that this should cause much change in how we judge and punish criminal acts, but just food for thought.