A person cannot make a valid will unless he has testamentary capacity, meaning that he is legally competent to create the will. You must be at least 18 years old and be "of sound mind and memory" to create a will. If you cannot articulate your wishes or have trouble recognizing close friends and family, you may not have the testamentary capacity necessary to draft your will. The people who witness your will must be able to tell the court later that you were of sound mind when you signed the will.
In Illinois, your will must be in writing and signed by you or by another person at your direction and in your presence. Your signing must be witnessed by at least two credible witnesses who do not have an interest in your will. For example, if one of your witnesses stands to inherit from you under the terms of the will, you must have three witnesses — two in addition to the one interested witness. Illinois does not recognize holographic wills — wills written entirely by hand - if they are not witnessed. Therefore, your will can be in your own handwriting, but it must be witnessed as if it were typewritten.
Revocations and Alterations
In Illinois, you can revoke, or withdraw, your will by destroying it, making another will in which you state you are revoking the prior will, or by making a later will that is inconsistent with the prior will. The will that is most recent will control what happens after you die. A will can also be changed by creating a codicil as long as the codicil otherwise meets Illinois’ will requirements. A codicil is a document that changes only a small part of the will rather than revoking or changing the entire document.
If an Illinois probate court declares a will invalid, perhaps because it was not properly witnessed, the deceased person’s estate is distributed according to Illinois laws of intestate succession. These laws provide a default method for an estate to be distributed if there is no valid will. For example, if you have a surviving spouse and child, each will receive half of your estate under state law.