People have the right to defend themselves when they are attacked or they feel in danger, this is known as self-defense. Every state, including Illinois, has different laws that define what self-defense means. In Illinois, you can use reasonable force to defend yourself or someone else, or to defend your home or other property.
In each case the following conditions must exist to justify the use of force:
There was imminent danger or threat to you, someone else, or your property;
The threat was unlawful;
You believed that a danger existed that required force; and
You used force that was equal to the threat.
You cannot claim self-defense if you are the aggressor. You also cannot overreact, or act unreasonably, in defending yourself.
There are 2 levels of force under the self defense laws:
Regular force: Force that prevents someone from moving or acting normally and
Deadly force: Force that causes or is intended to cause serious bodily harm or death
Regular force
You can use regular force to defend yourself or someone else, against an attack or entry into a home, or any other type of property.
Deadly force
Defense of person
If you’re defending yourself or someone else, you can use deadly force if you reasonably believe it’s necessary to prevent:
Imminent death or great bodily harm to yourself or another person, or
A forcible felony (e.g. sexual assault, battery, murder, robbery, arson).
Defense of home
You can use deadly force to prevent an assault or threat of violence against yourself or someone else in a home or other building, but only if
You use it against someone who is trying to enter in a violent manner or
You reasonably believe that such force is necessary to prevent a forcible felony in the building.
Defense of property
Deadly force is generally not allowed to use when you are protecting your own personal property of real property. You can use deadly force, however, only if you reasonably believe that such force is necessary to prevent the commission of a forcible felony.
Source: www.illinoislegalaid.org