Is the web site for the Cal Dept of Corrections. It shows 37% of prisoners Hispanic, v. 32% of population. So pop of california is over 11 million Hispanics, and 4 million is the highest estimate (way above the Census estimate) of illegals, so maybe 20% of all prisoners being illegal aliens would be about right. Also note that hispanics are more concentrated in the more crime-prone younger ages [not many criminals among the Leisure World crowd, of whatever race], so the age comparable comparison is even closer to parity.
All crime is still a huge problem -- is I said earlier, the trick is to get a policy to keep the productive and keep out the criminals and moochers.
I wonder if that includes local and county jails as well: ie. the L.A. county jail.