It's certainly a purely theoretical fate. I have zero reason to believe undocumented people are more dangerous than citizens. I mean, intuitively, they risk so much more - namely deportation and torture. If I followed a Republican philosophy of tough on crime, I would then say they must be committing less crime.
Do we have any reason to believe they're more dangerous? And I mean real reasons, like statistics. No Patrick, "they're vaguely brown" is not a real reason. No Patrick, "homogeneous population" isn't a real reason either.