I have dealt with situations like this. You can divorce a person who has been declared mentally incompetent. The mentally incompetent person will have to have a guardian to protect that spouse's interests. The guardian acts on behalf of the mentally incompetent person. There are normally attorneys representing both parties. I suggest that you contact a local family law attorney in your area for more specific advice and information. Good luck to you.
Henry Gornbein
Henry is correct. Because a person who is legally mentally incompetent cannot be "available" to negotiate a settlement, someone else must stand in her or his place. Procedure varies from county to county on the appointment of a guardian for such a person. If the mentally incompetent spouse already has a guardian, he or she can hire an attorney (or ask the court to appoint one if the ward is indigent) so that the case can proceed with the interests of the incompetent person taken into account. If no guardian has been appointed, one will have to be appointed in the Probate Court and then the divorce can proceed. In many courts, the Family Court assignment of the divorce case will be to the same judge so that the "one family, one court" rule is respected. I will be presenting on this topic at the upcoming ICLE Family Law Institute in November.