There continues to be a great deal of confusion as it relates to what it means to be "insane". This confusion exists for a variety of reasons, perhaps the most important being that the psychological definition of insane and the legal definition of insane does not necessarily track together. Insanity is defined and treated differently than mental illness by the courts as well.
As a starting point, Illinois law states a person is insane if, at the time of a crime and as a result of mental disease or defect, he lacks substantial capacity to appreciate the criminality of his conduct. See 720 ILCS 5/6-2(a). Put another way,if a person commits a crime and cannot understand what he did was wrong, he would be deemed to be insane.
In my experience, insanity is generally a result of a biological cause. For example, a brain tumor may cause a person to become violent for no apparent reason. Disorganized thoughts resulting from Schizophrenia may have so debilitated a person they do not understand theft is wrong. Another example would be a person who is so profoundly mentally retarded they cannot understand right from wrong. Occasionally, insanity may result from another source such as medicine. An example of this could be a doctor placing a person on a new type of medication with the medication causing a person to temporarily lose the ability to know right from wrong. The key is that the person cannot understand what they are doing is wrong.
Insanity does not have to be permanent, it can be temporary. Many conditions can be regulated to a greater or lesser degree by medication, sometimes surgeries can be performed to return a person to "normal".
Next time we'll discuss "mental illness", what it is, and how it compares to "insanity" in Illinois courts.