Sounds harsh but if the "trust" wasn't there and illegal bangers preyed on illegal aliens maybe they'd pack up and go home.
LA has probably a million illegals.
You can’t run a city when a million of its inhabitants are afraid to talk to the police. That will only develop an underworld ghetto run by criminals.
Hence, the illegals have to know that they can contact the police and even testify in court without being prosecuted
because of their illegal status.
When most law abiding people realize that they can't trust the government and their agents to uphold the law, soon they will give up in frustration and take the law into their own hands. That will be much worse.