He was a trial lawyer for 30 years, taught law school classes and seminars and then spent seven years on the Cook County Circuit Court bench.And although he has loved working in a courtroom, Associate Judge Michael R. Panter has decided to step down and “try another challenge.”Panter will leave his Daley Center seat in the Law Division on Sept. 28. After that, he’s off into the mediation field, where he said he can continue to do what he has enjoyed since he was appointed in 2008 — working with …