Impeachment is covered in the Illinois Constitution in
Article 4, Section 14, which states:

"The House of Representatives has the sole power to conduct legislative investigations to determine the existence of cause for impeachment and, by the vote of a majority of the members elected, to impeach Executive and Judicial officers. Impeachments shall be tried by the Senate. When sitting for that purpose, Senators shall be upon oath, or affirmation, to do justice according to law. If the Governor is tried, the Chief Justice of the Supreme Court shall preside. No person shall be convicted without the concurrence of two-thirds of the Senators elected. Judgment shall not extend beyond removal from office and disqualification to hold any public office of this State. An impeached officer, whether convicted or acquitted, shall be liable to prosecution, trial, judgment and punishment according to law."

There are several key points to this language.

• Only the Illinois House can conduct a legislative investigation to determine if sufficient cause for impeachment exists;
  
• Only the Illinois House can impeach (charge) executive and judicial branch officials;
  
• It requires a majority in the House to impeach an official;
  
• Only the Senate can conduct the trial, following an impeachment;
  
• For the trial, Senators must take an oath that they will do justice according to the law;
  
• If it is the Governor that is being tried, the Chief Justice of the Supreme Court presides (This is different from the normal procedure of the Senate, in which every two years, the members of the Senate elect a President who presides over the body);
  
• It requires a two-thirds vote of the Illinois Senate (the same as the U.S. Senate) to convict;
  
• The only punishment available is removal from office and being prohibited from holding any other public office;
  
• Impeachment is no substitute for criminal prosecution. Whether or not a public official has been impeached and/or convicted has no bearing on any criminal proceeding. It neither protects the individual from further prosecution or increases the likelihood of prosecution.

More details on the Illinois Constitution's treatment of impeachment is available in a Legislative Research Unit paper on Impeachment in Illinois.