Here's the sad thing about this story. In 2012, not long after his arrest the Illinois House of Representatives voted to expell Derrick Smith from that chamber. Unfortunately even after recruiting a Democrat - and having him run as a member of a new party - the voters of Smith's district sent him right back to the seat he had been expelled from.
In this year's primary he was supported by his party leaders. While it seems quite counterintuitive, it may well make sense if you want to protect the overall numbers of your caucus and without causing a circus of finding someone to replace one of your members. So it is now, while he's waiting to stand trial Rep. Smith remains a member of the Illinois General Assembly!
It's interesting that he knew he was wrong and said as much to the FBI agents who interviewed him. Now this is certainly one of those times where instead of running your mouth you may need to talk to an attorney.