D.C. Code § 47-1809.01: Tax on estates and trusts — Residency definitions.

For the purposes of this subchapter, estates and trusts are: (1) Resident estates or trusts, or (2) nonresident estates or trusts. If the decedent was at the time of his death domiciled within the District, his estate is a resident estate, and any trust created by his will is a resident trust. If the decedent was not at the time of his death domiciled within the District, his estate is a nonresident estate, and any trust created by his will is a nonresident trust. If the creator of a trust was at the time the trust was created domiciled within the District, or if the trust consists of property of a person domiciled within the District, the trust is a resident trust. If the creator of the trust was not at the time the trust was created domiciled within the District, the trust is a nonresident trust. If the trust resulted from the dissolution of a corporation organized under the laws of the District of Columbia the trust is a resident trust. If the trust resulted from the dissolution of a foreign corporation, the trust is a nonresident trust.