(a) Except as provided by Subsection (c), if a devisee under a will is also a subscribing witness to the will and the will cannot be otherwise established:
(1) the bequest is void; and
(2) the subscribing witness shall be allowed and compelled to appear and give the witness's testimony in the same manner as if the bequest to the witness had not been made.
(b) Notwithstanding Subsection (a), if the subscribing witness described by that subsection would have been entitled to a share of the testator's estate had the testator died intestate, the witness is entitled to as much of that share as does not exceed the value of the bequest to the witness under the will.
(c) If the testimony of a subscribing witness described by Subsection (a) proving the will is corroborated by at least one disinterested and credible person who testifies that the subscribing witness's testimony is true and correct:
(1) the bequest to the subscribing witness is not void under Subsection (a); and
(2) the subscribing witness is not regarded as an incompetent or noncredible witness under Subchapters B and C, Chapter 251.
Official text of the Texas Estates Code as published by the Texas Legislative Council.