And from what I've read, in many states, you can legally "establish" a new name for yourself simply by beginning to use that new name [i.e. in many states, you don't have to go through a formal legal name change - you can just start using a new name, and kinda/sorta establish that new name via "common law"].
What's important here is that he LIED to the Illinois State Supreme Court, and the really, REALLY, REALLY important question now is whether he ever travelled on an Indonesian passport after he became an adult [remember, Indonesia did NOT recognize dual-citizenship].
To have lied, he would have had to have known about his registration under this name. That's going to be tough to prove.
My parents could have registered me for school under a different name, for all I know. I never went back and checked my school paperwork when I was filling out my bar applications, either.