The Maricopa County Attorney’s Office Found that 21.8% of Felonies Sentenced in Maricopa County Superior Court were Committed by Illegal Aliens, More than Twice Their Share of the Population. Mexican Nationals alone made up 13% of Inmates in State Prison System.

A study of 2008 data by the Maricopa County Attorney’s Office found that while illegal aliens made up 9 percent of Arizona’s population, illegal aliens accounted for 21.8 percent of felonies sentenced in Maricopa County Superior Court.

In 2008, there were 5,173 Mexican Nationals in the state prison system out of 40,188 prisoners — 13% of the state prison population.

Some other data from the report is available here.