The following is an excerpt from an article at Reason that discusses immigration in Arizona:
The state has an estimated 460,000 illegal immigrants. But contrary to myth, they have not brought an epidemic of murder and mayhem with them. Surprise of surprises, the state has gotten safer.
Over the last decade, the violent crime rate has dropped by 19 percent, while property crime is down by 20 percent. Crime has also declined in the rest of the country, but not as fast as in Arizona.