> It can’t be destroying evidence if there’s no case or charge being pressed for which that material would be evidence.

(IAAL, not legal advice, consult your own lawyer)

Where’d you get that idea? That’s not the law. As soon as there is reasonable suspicion that a crime has been committed, and the law enforcement encounter occurs, that’s the threshold for when preservation of evidence begins. It doesn’t matter whether it might not have ultimately resulted in a criminal charge. You cannot intentionally interfere with a lawful investigation, in any way, full stop.