Los Angeles Police Chief, William Bratton, published an opinion piece that explains why he did not allow the police department to participate in a Department of Homeland Security program that gives local law enforcement agencies the powers of federal immigration agents.
Some in Los Angeles have asked why the LAPD doesn't participate. My officers can't prevent or solve crimes if victims or witnesses are unwilling to talk to us because of the fear of being deported. That basic fact led to the implementation almost 30 years ago of the LAPD's policy on immigrants, which has come to be known as Special Order 40. The order prohibits LAPD officers from initiating contact with someone solely to determine whether they are in the country legally. The philosophy that underlies that policy is simple: Criminals are the biggest benefactors when immigrants fear the police. We can't solve crimes that aren't reported because the victims are afraid to come forward to the police.
The idea of engaging all members of the public in reporting crime and identifying criminals not only helps us with short- and medium-term goals of reducing crime; it helps improve relations with community members. We all have an interest in helping our young people develop into healthy, educated and law-abiding adults. Breeding fear and distrust of authority among some of our children could increase rates of crime, violence and disorder as those children grow up to become fearful and distrustful adolescents and adults. That is why the Los Angeles Police Department has not participated in 287(g) and the federal government is not pressuring the department to do so.
Americans want a solution to our immigration dilemma, as do law enforcement officials across this nation. But the solution isn't turning every local police department into an arm of Immigration and Customs Enforcement.
Check out the whole article. He makes some interesting points.