Jim Dey: "The onetime chief of staff to former Illinois House Speaker Michael Madigan had invoked his constitutional right to remain silent both about the Commonwealth Edison bribery scandal and the close relationship between two alleged co-conspirators — Madigan, the alleged ringleader, and Michael McClain, a Madigan confidant who’s already been convicted in the scheme. But the feds nullified Mapes’ right to remain silent by giving him immunity."