A former Jenkens & Gilchrist lawyer pleaded guilty Tuesday to conspiracy and tax evasion as part of a cooperation agreement with the U.S. government.

Erwin Mayer, 47, entered guilty pleas and gave a long allocution before Southern District of New York Judge William Pauley, admitting that he helped market and defend illegal tax shelters in a scheme prosecutors say cost the government billions. “I am filled with shame and remorse for what I did in J&G’s tax shelter practice,” said the one-time Chicago lawyer.