Several forms of protection against upcaste offenses exist. First, employment and patronage tend to run upcaste. A factory may include a thousand Workers, with Indigenes as managers, and the factory as a whole owned by a Compatriot or a Citizen. If a Worker thus employed is damaged by someone upcaste, the assault is not a crime, but the subsequent loss of productivity to the factory can be prosecuted as a crime on behalf of the upcaste factory owner.
Imagine the way it works as something like a big Vegas casino run by the mafia. They're not going to stand for muggers going after people in the casino, that's bad for business; the mugger is attacking not just the casino patron, but the income of the casino owner. On the other hand, if they catch someone cheating, then he's likely to get seriously roughed up; the rules work differently in that direction.
Permament upcasting requires a Very Large Fee. However, temporary upcastes can be registered, for (generally) smaller fees, for a specific action (assault, robbery, brawling, etc). One cannot actually upcaste for murder, and murder is nearly always justified as an offense to some Citizen, if only to their peace of mind.