Research your state’s available grounds for divorce to determine how you can file based on your spouse’s mental condition. In some states, an insanity ground may be prohibitive. Some jurisdictions require that your spouse remain institutionalized for up to five years before you can file. Others require a doctor’s certification that your spouse’s mental condition is not likely to improve. If your situation doesn’t qualify for your state’s guidelines, or if it would be an uphill battle for you to prove his mental incapacity to the court, confer with an attorney to find out if you can use another ground instead.
Meet with your spouse’s family members. Find out if any of them would be willing to take on the responsibility of acting as his conservator or guardian. Depending on the severity of your spouse’s mental state and how capable he is of making rational decisions for himself, the court may require that he have someone to legally deal with the details of the divorce for him.
File a petition or complaint for divorce as you normally would, if your spouse were of sound mind. Use the ground you’ve decided on after consulting with an attorney. Serve it on your spouse according to your state's laws, or on the director of the medical facility if he's institutionalized. If one of his family members has agreed to be his guardian, serve a copy on that individual as well.
Petition the court to appoint a guardian ad litem for your spouse if no family member is willing to take on the responsibility. This will generally involve filing a motion under the docket number of your complaint for divorce. Serve a copy of your motion on your spouse so he can attend the hearing, if he’s not living in an institution. If he is institutionalized, serve a copy on the director of the facility.
Attend the hearing for your motion. If you have any medical records or doctor’s reports for your spouse, make copies and take them with you. The judge will either decide that your spouse is competent enough to handle the divorce on his own, or he will appoint a guardian ad litem for him. A guardian ad litem is someone appointed by the court, often an attorney, to look out for your spouse’s best interests. In some states, the court will appoint a guardian ad litem even if one of your spouse’s family members is also acting as his guardian. After this point, your divorce should proceed along normal channels.