The laws in Illinois are complex and strictly enforced, as is the case throughout the United States. One form of offense that is particularly commonly reported is assault, often in conjunction with battery. However, many people are unsure of the difference, making it particularly difficult for them to form their defense.
There are various rules surrounding both harm and intent to harm. In fact, in some cases accidentally injuring someone can still get you into trouble if you intended to touch them against their will. For an assault to have occurred, you simply have to have made someone expect an act of battery. This can include violent gestures or motioning as if to strike someone. If you actually make contact, however lightly, this then becomes an act of battery.
It is also important to remember that you do not have to have touched the person's body for battery to have occurred. As is explained in this article on assault, accessories, clothes and anything else on an individual at the time of the crime count as part of their extended person. Acts such as grabbing someone's clothes, or knocking a drink over all count as battery, as long as there was intent to cause some form of contact.
Conversely, if you simply are clumsy and did not intend to touch them or anyone else, then it is not a crime, simply an unfortunate accident. Of course, you may still need to prove this if the person in question chooses to challenge you over it. An attorney may be invaluable in this situation. He or she can help you understand the allegations against you and might be able to assist you in building your defense.