The question of the crime rate of immigrants, legal and illegal, is not easy to assess. On the other hand, it is easy to assess the crime rate of minority groups, some of whom are largely populated with first, second, and third generation immigration.
For example, Asians contribute less to crime than others, including Whites. On the other end are hispanics, who do contribute to much higher crime rates. Logically then, one ought to be guarded about hispanic immigration, because they are much more likely to become criminals.
Regarding the criminality of first generation immmigration, the statistics are only suggestive, not conclusive. However one ought to note that the Homeland Security Department, as a part of their Secure Communities program, estimated that 20 percent of those incarcerated (at all levels of government), are foreign born (only 12 or 13 percen to the US is foreign born). And the Fentress Corporation in its study of 8.2 million inmate record in jails and prisons found 22 percent (2004) were foreign born.
In a study conducted by the panelists and authors (linked below) they found that "in four of the six counties where we had good 287(g) data and possibly five, really, it does appear that the illegal immigrants make up a much larger fraction of the jail population than they do the overall population of adults in that community. ...Maricopa County, it appears that 22 percent of felons were found to be illegal immigrants and illegals seem to be only about 10 percent of that county’s adult population. In another example, in Lake County, Illinois, illegals are 19 percent of jail inmates, but only 6 percent of the local adult population."http://cis.org/Transcripts/ImmigrationAndCrimePanel
Also one should note that the evidence of criminality may be understated:
•From 1998 to 2007, 816,000 criminal aliens were removed from the United States because of a criminal charge or conviction. This is equal to about one-fifth of the nation’s total jail and prison population. These figures do not include those removed for the lesser offense of living or working in the country illegally. The removal and deportation of large numbers of criminal aliens may reduce immigrant incarceration rates because many will not return and re-offend, as is the case with many native-born criminals.
But as I said, we can measure crime rates among minority groups, and among minority groups whose presence in America is due to immigration (rather than slavery) Latinos rank highest. That alone suggests that we should be wary and restrictive of this group.