Texas Rule of Evidence 611 states that a witness "may be cross- examined on any matter relevant to any issue in the case, including credibility." TEX. R. EVID. 611.
Thus, a trial judge may allow either party to show any relevant fact that establishes or tends to establish bias on the part of the witness. See London v. State, 739 S.W.2d 842, 846 (Tex. 1987).
Friendship or leanings of the witnesses and those associated with them toward any party or issue is relevant to any inquiry into bias. Hinojosa v. State, 788 S.W.2d 594, 600 (Tex. App.-- Corpus Christi 1990, no pet.).
In Norrid v. State, 925 S.W.2d 342 (Tex. App.--Fort Worth 1996, no pet.), the defendant was on trial for solicitation of capital murder. Id. at 344.
On cross-examination of the victim, the defendant tried to ask about her psychological treatment, alcoholism, and sexual preferences. Id. at 346.
In affirming the trial judge's decision to exclude such cross- examination, the Fort Worth Court of Appeals stated that it was not clear how such testimony indicated the victim's bias or motivation. Id. at 347.