[mklim]

I don't think those are mutually exclusive. It would make sense that a classist/segregated society would both cause and be reinforced by elevated crime rates in the lower classes. Less legal opportunities for the lower classes to make money, and if they were poorer they'd have a more desperate need for immediate wealth than the upper classes, so that would make crime more attractive for them on average. And reports of those crimes would be a reason for the upper classes to justify their classism/segregation to themselves (ie: "of course those people just can't be allowed into polite society, look how dangerous they are") and lead to them enforcing the segregation more strictly. And that's not even taking into account selective prosecution/policing by law enforcement.