From the Orange County Register:
For more than a year the Orange County Sheriff's Department has had specially-trained deputies screening county jail inmates for immigration status. Arrestees who are determined to be in this country illegally are detained and turned over to federal immigration authorities after their criminal cases are resolved.
Out of about 68,000 arrestees who were screened between Jan. 2007 and January of this year, 4,683 were found to be illegal immigrants, or about 7 percent of all screened arrestees. (About 3,000 of them had been arrested for non-immigration-related felonies, the rest for non-immigration misdemeanors.)
Read it all right here.