In Carpenter v. State, 979 S.W.2d 633 (Tex. Crim. App. 1998), the defendant sought to impeach a State's witness with evidence of a pending federal conspiracy charge, under the theory that the pending charge might make the witness inclined to testify favorably for the State to obtain some benefit or avoid some detriment in the federal case. Id. at 635. The trial court, acting upon the objection of the State, did not allow evidence of the pending federal charge before the jury. See id. The Court of Criminal Appeals affirmed this ruling, reasoning that for an impeachment by evidence of pending charges to be admissible, a defendant must establish some causal connection or logical relationship between the pending charges and the witness' potential bias or prejudice for the State, or testimony at trial. Id. at 634. The defendant in Carpenter simply had not shown why prosecution by the federal government for conspiracy would tend to show that the witness' testimony in the unrelated state prosecution might be biased. Id. at 635. There was speculation offered that it was possible that the witness believed his testimony in this case would be of some benefit in the federal prosecution, but there was no evidence that this was what the witness thought or that the testimony might actually be of some benefit to him in the federal prosecution. Id. The Court concluded that the defendant simply had not provided any causal connection or logical relationship between the pending federal charges and the witness' testimony at trial. Id. The Court of criminal appeals held that the trial court did not abuse its discretion by denying cross-examination into pending charges against a witness. Carpenter, 979 S.W.2d at 635. The court concluded that appellant could not provide any basis, other than an unsubstantiated assertion, for her suggestion that the witness, who was subject to federal criminal charges unrelated to the case against Carpenter, was biased. Id. Without such a showing, there was nothing in the record to suggest that the witness' testimony would be relevant to the charges against appellant. Id. at 634. In Carpenter v. State, evidence to show bias of a State witness in state court was properly disallowed when the alleged bias concerned unrelated pending federal felony charges. Carpenter, 979 S.W.2d at 635. In Carpenter, the defendant failed to establish a nexus or logical relationship between the pending federal charges and the witness's testimony, because the federal charge was unrelated to the State's prosecution in which the witness was involved. Id. Further, the bare assertion that the witness may have believed his testimony in state court would somehow benefit him in his federal case was insufficient to allow impeachment on that point. Id.