I really don't know why it is that the Houston Police Officers Union has decided it wants HPD to be different from every other urban police force in the state and start questioning residents about their immigration status. The reasons why this is a bad idea are spelled out in the story, but let me briefly summarize: If people believe that by talking to the cops something bad might happen to them or their families, then they won't talk to the cops. That means that victims of crime, witnesses to crimes, people with information about specific crimes or criminals, they'll just clam up and not get involved. It shouldn't take any great insight to realize that this is not conducive to public safety, yet it's what HPOU wants. I don't understand it any more than you do.
Perhaps the problem here is that they start off with a faulty premise.
[Gary Blankinship, president of the Houston Police Officers Union] said 1,433 of the 7,700 inmates processed through the Houston city jail in February identified themselves as noncitizens, although he does not know how many were illegal immigrants.
"I can't help but believe a large number were in this country illegally," he said. "If we had to put our hands on 1,433 fewer people a month, that would free up police for other tasks."