"Sybil": When mental illness destroys a marriage and raises child custody concerns

Mental illness can, and often does, destroy a person’s life, and their marriage. The 1976 movie, Sybil, starring Sally Field has been getting much replay and is one of the hot trends on Google this week and it made me start to think about mental illness in the context of divorce, and of custody of children.
Sybil, the movie, is based on a real story of a young woman by the name of Shirley Ardell Mason and her story as told in a book by the same name written by Flora Rheta Schrieber in 1976. It has to do with a woman with multiple personality disorder, and “disassociative identity disorder.” No, I haven’t seen the movie. Have you? But. I was just wondering. 
What happens if you marry someone with multiple personality disorder, or disassociative identity disorder, or some other type of mental illness? Are you stuck? And what about the kids? Should this person have access to the children? Well let’s take each issue in turn.
First, are you stuck with being married to “Sybil”?
Well, in New York, if all you have to go on is “mental illness” you technically could be stuck because there is no explicit ground that grants you a divorce on the basis of “mental illness” strictly speaking. The grounds for divorce in New York are: abandonment, constructive abandonment, imprisonment, adultery, separation agreement, judgment of separation, and cruel and inhuman treatment.
Now. While, as I said, there is no grounds for divorce that explicitly gets you a divorce on “mental illness”, the last ground– cruel and inhuman treatment — does give you room to play. Especially if your marriage is not a “long term” marriage. Long term marriages are treated differently, and if you have been in a long term marriage, it could be more difficult for you to win a cruel and inhuman treatment divorce action. You have a much higher degree of proof that is required.  See, example, Brady v. Brady 64 NY 2d 339 and Hessen v. Hessen 33 NY 2d 406. Oh, you can still get a divorce even if you have a long marriage. But your burden of proof is higher is all I’m saying.
But if your marriage is not so long, under 10 years, for example, and the “cruel acts” are less than five years old (there’s a 5 year statute of limitations on allegations of cruelty) then you are in business. You can argue, not necessarily that your spouse is “crazy”, but that your spouse treats you “cruelly”. It’s a semantic technicality. But, again, if you want the divorce, you have to word it in a way that fits the statute. I mean, everybody recognizes that it may be madness that makes a husband beat his wife. But the wife is not going to ask for a divorce because her husband is mad. She is going to ask for the divorce because he abuses her physically, or “treats her cruelly.” (Same is true for husbands with crazy wives, btw.)
It will help a lot to have corroborating witnesses to these allegations.
Now. Other than a divorce, mental illness may be a basis for an annulment. I mean, if you are married to a Sybil this could be a basis for annulment. First of all, you can get an annulment to declare the marriage void for want of understanding. An annulment to declare a marriage “void” for want of understanding could be brought by either party to the marriage, or by a third party with an interest in the marriage, such as a family member.
That should be distinguished from the annulment due to “incurable mental illness.” Such a cause of action can be brought if the “Sybil” has been declared incurable insane, and the mental illness has been going on for five years or more.  The Sybil could not be the one bringing such a divorce action, however. Nor could they necessarily defend the action. The court is likely to appoint a guardian ad litem for such a person.
You are going to need at least 3 corroborating physicians to say that your spouse is a Sybil in order to get an annulment on this basis.
Okay. Now, very briefly, custody.
Would the court grant custody to a “Sybil” mother or father? I strongly doubt that any court of competent jurisdiction would. Particularly if you have corroborating medical testimony from doctors that states this person has a serious mental illness. I don’t think any court would give such a parent custody because it would not be in the “best interest” of the child to do so. If the other parent (who is not a “Sybil”) cannot handle custody, the children will probably be placed in foster care, or put up for adoption – depending on the severity of the mental illness.
If the parent is only marginally mentally incapacitated, then the parent would be ordered to get treatment, and probably receive supervised visitation with the children, until such time that the condition improves. If the condition does not improve, or worsens, then a petition to terminate the parental right may be made at some point and the children would be put up for adoption — assuming the other parent is not available or competent to provide custodial care for the child(ren).