Justice Ellis began his legal career in private practice in Chicago in 1993, where he specialized in commercial litigation and constitutional law. In 2007, he began serving as Chief Counsel to the Speaker of the Illinois House of Representatives, where he advised the Speaker on constitutional and legislative issues and also served as the House Parliamentarian who decided matters of parliamentary procedure. In 2009, he served as Counsel to the House Special Investigative Committee considering the impeachment of Governor Rod Blagojevich. He then served as the House Prosecutor who tried and convicted Governor Blagojevich in the Impeachment Trial before the Illinois Senate. Prior to becoming a judge, he litigated several constitutional issues of first impression in Illinois, principally regarding the separation of powers between the legislative and executive branches of state government. He was elected to the Illinois Appellate Court in 2014 and took office December 1, 2014.