He's accused of trying to protect former Illinois House Speaker Michael Madigan when he was his chief of staff.
For the decades he served as Madigan's chief of staff, Mapes was known in Springfield to be very meticulous and dedicated to details.
Yet, prosecutors said when it came to answering basic questions during a grand jury proceeding about Madigan's longtime relationship with the former House speaker's trusted advisor, Mike McClain, Mapes lied over and over.
In her closing argument, Assistant U.S. Attorney Julia Schwartz told jurors, "Mr. Mapes was no dummy, he knew exactly what was being asked of him, and he tried to shut down any further questioning by pretending he didn't remember, and that was a lie."
Mapes was given full immunity by prosecutors during their investigation into a bribery scheme involving Madigan and McClain.
Schwartz said, "Mr. Mapes could have been a star witness for the government."
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Instead, "he decided to stay in the fox hole and protect the boss, something he has done for 25 years."
Presenting 15 witnesses and dozens of wiretapped phone conversations, prosecutors tried to show the very close relationship among Mapes, McClain and Madigan.
The government said Mapes brazenly lied to the grand jury when asked several similar questions about the nature of Madigan and McClain's relationship.
In his closing argument, defense attorney Andrew Porter told jurors, Mapes "couldn't remember what he didn't know."
Porter said during the grand jury proceedings, Mapes was "not trying to protect the boss; he was trying to answer honesty and carefully."
Describing Madigan as a very private person who prefers one-on-one conversations, Porter argued, "Tim Mapes didn't know what Madigan and McClain were saying in their private conversations."
Porter said Mapes is charged with perjury over not recalling insignificant past legal events that had nothing to do with criminal activity involving Madigan and McClain.