The issue first is whether your mother has an enforceable right to the $85K, then the issue would be if that right was assignable and if it survived her death. That is an issue for a Family Law attorney. If she does have a right, she can do an assignment and assign her interest in that claim to her trust.
As to your father's trust, a self-settled trust does not provide creditor protection.
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Transferring the home into his own trust does not provide any protection against a lien. Child support debt is highly collectible. Your mother should contact the Department of Child Support Services or a private family law attorney regarding collecting these monies. If he has any income, it should be attached (garnished, have the wages withheld) in addition to any liens that may already be in place.
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I would create a trust and draft a will as well. I don't think you can put a lien on the house into a trust, but if she leaves a will as well, leaving everything that she has to you, you will inherit it. What I would do if I were her, though, is to contact the Marshal where the lien is issued and have him execute the judgment. Marshal can force your father to sell his home so you can collect on child support.
Please contact my law office at 718-333-2394 or visit my website at www.BrooklynTrustandWill.com for more information about this answer. Inna Fershteyn Law Office of Inna Fershteyn, P.C. 1517 Voorhies Ave, 4th Floor Brooklyn, NY 11235 (718) 333-2394 www.BrooklynTrustandWill.com