Genuine question since the article doesn't mention it -- how does the AP know conversations were destroyed? I would assume a properly-designed, E2E encrypted app like Signal wouldn't leave obvious evidence of shredded conversations.
My guess is it is based on testimony from some of the involved parties that they had these conversations and then later the chat histories were gone? But I'd like to know more.
Moreover, do we know the conversations were destroyed AFTER they were ordered to preserve them and not just routinely destroyed?