On the night in question, four men entered a commercial building and pushed a safe out of a second-floor window and into the building's yard. The safe was too heavy to move, so they went for assistance and enlisted the help of Richard Zierlion (defendant) and one other man. The burglars, with their assistants, returned to the yard. Police arrived and arrested the men after a brief gunfight in which Zierlion was wounded and the other assistant killed. The State of Illinois prosecuted Zierlion for burglary, relying on an Illinois statute that provided that one who aids, abets, assists, advises, or encourages the perpetrator of a crime is a principal in the crime. The trial judge, sitting without a jury, convicted Zierlion. He appealed his conviction to the Illinois Supreme Court.