Not to be picky here, but you haven't cited any DoJ figures. You are citing NEWSMAX.com, which even though it has a "conservative" slant, sadly ranks even below the New York Times in terms of accuracy and fact checking. The actuat statistics are out there on the web at some .gov site. It would just take some time to track them down.
The closest I see to an "informed" statistic was the quote from Pete Wilson that disputes your 40% figure.
One in five in our prison population were illegal immigrants who had been convicted of a felony after entering the country illegally."
That's 20%, not 40%
Not to be pickier, but the statistic that the Newsmax article uses is from an Investors Business Daily article written in March of 2005. Would you impeach their reporting as well? But, since you wanted the statistics from a government site, I will endeavor to find the statistic elsewhere. 40% or more seems perfectly plausible in California. Come and visit our state some time and see for yourself. :)