• Committing a felony in Illinois will result in imprisonment.handcuffs image by William Berry from Fotolia.com
  
  The state of Illinois categorizes criminal offenses as either a petty offense, misdemeanor or felony. While petty offenses are subject to only a fine and misdemeanors are subject to a fine and a maximum of one year in jail, felony offenses bring the stiffest penalties. Illinois has five classes of felonies, all subject to a minimum jail sentence of more than one year. In addition, Illinois has mandatory jail sentences for certain crimes.
  
  

Class 4 Felony

• The lowest level felony is the class 4 felony. A class 4 felony incurs a jail sentence of one to three years and a fine of up to $25,000, as of November 2010. Additionally, the offender is on parole for a period of one year after his release. Examples of class 4 felony offenses include aggravated assault and stalking.
  
  

Class 3 Felony

• The next level is the class 3 felony. Those guilty of a class 3 felony face to two to five years' imprisonment, as well as a fine of up to $25,000. The offender also receives a one-year parole after his release. Aggravated battery is an example of a class 3 felony.
  
  

Class 2 Felony

• Class 2 felony is the next highest felony class. A person who commits a class 2 felony is subject to three to seven years' imprisonment and a fine of up to $25,000. In addition to these penalties, the offender also receives two years of parole after release. Arson is one type of class 2 felony.
  
  

Class 1 Felony

• The second to the highest felony class in Illinois is the class 1 felony. A class 1 felony offense results in four to 15 years of incarceration and a fine of up to $25,000. After the offender completes his sentence, he will receive two years of parole. Criminal sexual assault and heroin or cocaine possession are types of class 1 felony.
  
  

Class X Felony

• The class X felony is the highest felony class in the state of Illinois and carries the stiffest penalties. Committing a class X will result in six to 30 years of imprisonment, as well as, a fine of up to $25,000. In addition to these penalties, the offender will receive three years of parole. Aggravated criminal sexual assault, solicitation of murder and armed robbery are types of class X felony offenses.