DT as you know simply means defaultly trusted members and I think that Theymos is the one that adds them to the DT list by himself. I came across a post this evening while I was surfing the forum. The post wason the meta board and Theymos reply was all over the thread I can't really remember if he was the OP of the thread but the thread had monthly updates of members of the forum that qualified for being a DT member that month.
Anyways I don't really know all the criterias to be selected by Theymos in the DT list but I know one of them is that you must be added by an already existing DT member preferably DT1 to be able to get a chance of getting on the list. And yes a newbie could someday be a DT member infact every DT member was once a newbie.
Is this the topic you're talking about?
1: Those newbies to the forum can reach the level of DT members if they adopt any system and how they progress.
2: What is a trust list? Could you explain to me about the trust list?
Regarding the questions, every member who is a DT today was once a Newbie. He didn't come here with all his reputation already, he was building it every day, contributing in some way to the forum. So, yes. Any member can become a DT.
Regarding the second question, @Crypto Library has already cited the topic that explains this and which is very enlightening.