Could cracking down on Illegal Immigration decrease crime rates?

http://www.worldnetdaily.com/index.php?fa=PAGE.printable&pageId=70728

"One of the wealthiest counties in America reports crime skyrocketing by 22 percent in the first quarter of 2008, while its neighbor saw crime plummet by 19.3 percent in the same time period – coinciding with a get-tough policy on illegal immigration."

Seems to me if the U.S. as a whole took a tough stance on illegal immigration, our crime rates nationwide would decrease. We would also see less heinous crimes like those commited by illegal immigrants in New Jersey (which shot four students in the head execution style) or San Francisco (MS-13 gangbanger shot a father and his two sons with an AK-47 for blocking traffic).